KR20070006093A - Li secondary battery - Google Patents

Abstract

Provided is a lithium secondary battery, which has a safety vent capable of being broken with ease under an increased internal pressure, and thus imparts improved safety to the battery. The lithium secondary battery(200) comprises: a wound electrode assembly(300) having a first electrode plate(310), a second electrode plate(320), and a separator(330) interposed between the first electrode plate and the second electrode plate; a casing(210) having a space in which the electrode assembly is received; a cap plate(410) coupled to the casing for sealing the casing and including a safety vent having a desired form of concave portion; and an electrode terminal connected electrically to the electrode assembly. The concave portion preferably takes the form of a cross.

Description

Lithium Secondary Battery

Figure 1a is a perspective view for explaining a conventional cap assembly.

FIG. 1B is a cross sectional view along line A-A in FIG. 1A;

Figure 2 is an exploded perspective view for explaining a lithium secondary battery according to an embodiment of the present invention.

Figure 3a is a perspective view for explaining a cap plate of a lithium secondary battery according to an embodiment of the present invention.

3B is a cross sectional view along line B-B in FIG. 3A;

(Explanation of symbols for main parts of drawing)

200; Lithium secondary battery 210; Lithium Secondary Battery Case

300; Electrode assembly 310; First electrode plate

315; First electrode tab 320; Second electrode plate

325; Second electrode tab 330; Separator

340; Insulating tape 400; Cap assembly

410, 500; Cap plates 411 and 510; Terminal through hole

412, 520; Electrolyte injection port 413; Bowl

415, 530; Safety van 531; waist

420; Terminal electrode 430; gasket

440; Insulation plate 450; Terminal plate

460; Insulated case 462; Electrolyte injection through hole

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having improved safety of a secondary battery by having a safety band that can be more easily broken when the internal pressure increases.

Recently, compact and lightweight electric / electronic devices such as cellular phones, notebook computers, camcorders, etc. have been actively developed and produced. These portable electric / electronic devices have a battery pack that can be operated in a place where no separate power source is provided. The built-in battery pack includes at least one battery therein for outputting a predetermined level of voltage for driving the portable electric / electronic device for a period of time.

In view of economical aspects, the battery pack employs a secondary battery capable of charging and discharging. Representative secondary batteries include lithium secondary batteries such as nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries.

In particular, the lithium secondary battery has an operating voltage of 3.6V, which is three times higher than nickel-cadmium batteries or nickel-hydrogen batteries, which are widely used as power sources for portable electronic equipment, and is rapidly expanding in terms of high energy density per unit weight. to be.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. In general, a battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to the type of electrolyte, and a battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. Moreover, although a lithium secondary battery is manufactured in various shapes, typical shapes include cylindrical shape, square shape, and pouch type.

Typically, the lithium ion secondary battery is positioned between the positive electrode plate coated with a positive electrode active material, the negative electrode plate coated with a negative electrode active material, and between the positive electrode plate and the negative electrode plate to prevent a short and to prevent lithium ions (Li-ion). A lithium ion secondary battery case accommodating the electrode assembly, an electrolyte solution injected into the lithium ion secondary battery case to allow lithium ions to move, and the like; .

The lithium ion secondary battery is coated with the positive electrode active material and the positive electrode tab is connected to the positive electrode tab, the negative electrode active material is coated, the negative electrode tab is connected to the negative electrode plate and the separator is laminated, and then wound to prepare an electrode assembly. In this case, the positive electrode active material is a composite oxide containing lithium (Li) as a main component, and in general, after mixing lithium carbonate and cobalt oxide in a ratio of 1.2: 1, LiCoO 2 formed by firing at 400 ℃ to 1000 ℃ do.

Then, the electrode assembly is accommodated in the case for the lithium secondary battery, and the cap assembly is assembled on the top of the case for the lithium secondary battery, thereby preventing the electrode assembly from being separated.

After the cap assembly is assembled to the lithium secondary battery case, an electrolyte solution is injected into the lithium ion secondary battery case and sealed to complete the lithium ion secondary battery.

Meanwhile, as shown in FIGS. 1A and 1B, the cap assembly includes a cap plate 100 in which a safety vent 110 is formed, and thus, the lithium secondary battery is formed due to a gas generated during charging of the lithium secondary battery. Prevents explosion due to rising internal pressure. That is, when the internal pressure of the lithium secondary battery rises, the safety vent 110 breaks the safety vent 110 so that the internal gas is discharged to the outside, thereby providing safety to the lithium secondary battery.

However, the lithium secondary battery as described above has a problem that the reaction speed of the safety van 110 may be slow because the internal pressure should be increased to a predetermined pressure or more even when the safety van 110 is provided.

In addition, when the response of the safety vent 110 is slow, there may be a problem such that the lithium secondary battery first explodes before the safety vent 110 is broken.

An object of the present invention is to solve the above problems of the prior art, the present invention is to provide a lithium secondary battery with improved safety of the secondary battery having a safety band that can be more easily broken when the internal pressure increases. There is a purpose.

The lithium secondary battery of the present invention for achieving the above object comprises a wound electrode assembly having a separator interposed between the first electrode plate, the second electrode plate, the first electrode plate and the second electrode plate; A case having a space for accommodating the electrode assembly; And a cap plate having a safety plate with a predetermined recess formed therein and coupled to the case, and a cap assembly having an electrode terminal electrically connected to the electrode assembly.

Preferably, the recess is formed in a cross shape.

The cap plate may include a terminal through-hole into which the electrode terminal is inserted and an electrolyte inlet for injecting an electrolyte, and the safety vane may be formed on the opposite side of the electrolyte inlet based on the terminal through.

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

Like reference numerals in the drawings denote like elements.

2 is an exploded perspective view for describing a lithium secondary battery according to an embodiment of the present invention.

Referring to FIG. 2, the lithium secondary battery 200 according to the exemplary embodiment of the present invention includes a lithium secondary battery case 210 and a jelly-roll electrode assembly 300 accommodated in the lithium secondary battery case 210. ) And a cap assembly 400 coupled to an upper portion of the lithium secondary battery case 210.

The case of the lithium secondary battery 210 is formed of a metal can having a box shape having an approximately opened upper portion thereof, and may perform a role of a terminal itself.

The electrode assembly 300 is attached to any one of the first electrode tab 315 used as the positive electrode tab and the second electrode tab 325 used as the negative electrode tab, for example, the first electrode tab 315. The second electrode plate 320 to which the first electrode plate 310 and the other one of the first electrode tab 315 and the second electrode tab 325 are attached, for example, the second electrode tab 325. And, the separator 330 interposed between the first electrode plate 310 and the second electrode plate 320 is formed in a wound form, it is accommodated in the secondary battery case 210. In order to prevent a short circuit between the first electrode plate 310 and the second electrode plate 320 at the boundary where the first electrode tab 315 and the second electrode tab 325 are drawn out from the electrode assembly 300. Each is insulated by an insulating tape 340.

In addition, the first electrode plate 310 and the second electrode plate 320 have different polarities from each other, and at least one surface of each of the first electrode plate 310 and the second electrode plate 320 may be a positive electrode active material or a negative electrode. The active material is applied. In this case, a chalcogenide compound is used as the cathode active material, and complex metal oxides such as LiCoO 2, LiMn 2 O 4, LiNiO 2, LiNi 1-x Cox O 2 (0 <x <1), and LiMnO 2 are used. As the negative electrode active material, carbon (C) -based materials, Si, Sn, tin oxides, composite tin alloys, transition metal oxides, lithium metal nitrides, or lithium metal oxides are used. In addition, an electrode plate, for example, the first electrode plate 310 used as the anode electrode plate among the first electrode plate 310 and the second electrode plate 320, is made of aluminum (Al) material and a cathode electrode. The electrode plate used as the plate, for example, the second electrode plate 320 is made of a copper (Cu) material, the separator 330 generally uses polyethylene (PE) or polypropylene (PP), It does not limit the above material in the present invention.

The cap assembly 400 is provided with a flat cap plate 410 having a size and shape corresponding to the opening of the secondary battery case 210. A terminal through hole 411 is formed at the center of the cap plate 410, and an electrolyte injection hole 412 for injecting an electrolyte is formed at one side of the cap plate 410, and the electrolyte injection hole 412. ) Is combined with the bowl 413 is sealed. In addition, a safety vent 415 for providing safety to the lithium secondary battery 200 is formed at the other side of the electrolyte injection hole 412. In addition, a predetermined recess 415a is formed in the safety vent 415. This is for the safety vent 415 to be broken at a lower pressure when the internal pressure of the lithium secondary battery 200 rises. In addition, a first electrode tab 315 drawn from the first electrode plate 310 is welded to a lower surface of the cap plate 410.

An electrode terminal 420, for example, a negative electrode terminal, may be inserted into the terminal throughhole 411. The outer surface of the electrode terminal 420 is provided with a tube-shaped gasket 430 for electrical insulation with the cap plate 410. An insulating plate 440 is disposed on the bottom surface of the cap plate 410. The terminal plate 450 is provided on the bottom surface of the insulating plate 440.

The electrode terminal 420 is inserted through the terminal through hole 411 in a state in which the gasket 430 surrounds the outer circumferential surface. The bottom portion of the electrode terminal 420 is electrically connected to the terminal plate 450 with the insulating plate 440 interposed therebetween.

The second electrode tab 325 drawn from the second electrode plate 320 of the electrode assembly 300 is welded to the terminal plate 450 to be electrically connected to the terminal plate 450. Accordingly, the electrode terminal 420 has the same polarity as the second electrode plate 220 of the electrode assembly 300, for example, a cathode.

On the other hand, the upper surface of the electrode assembly 300 electrically insulates the electrode assembly 300 and the cap assembly 400, and at the same time an insulating case 460 that can cover the upper end of the electrode assembly 300 Is installed. The insulating case 460 is provided with an electrolyte injection hole 462 at a position corresponding to the electrolyte injection hole 412 of the cap plate 410, to inject the electrolyte solution. The insulating case 460 is an insulating polymer resin, preferably made of polypropylene, but the material is not limited in the embodiment of the present invention.

3A is a perspective view illustrating a cap plate of a rechargeable lithium battery according to one embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along line B-B of FIG. 3A.

3A and 3B, the cap plate 500 for a rechargeable lithium battery according to an embodiment of the present invention includes a terminal through hole 510 in which electrode terminals are inserted, an electrolyte injection hole 520 for injecting an electrolyte, and a secondary battery. It is made of a structure having a safety vent 530 to impart stability to.

In this case, the safety vent 530 is preferably formed on the opposite side of the electrolyte injection hole 520 on the basis of the terminal through hole 510 formed in the substantially center of the cap plate 500.

In addition, a predetermined recess 531 is further formed in the safety vent 530, and the recess 531 preferably includes a cross recess 531.

The safety vent 530 and the recess 531 are formed on the opposite side of the electrolyte injection hole 520 by pressing or the like on the basis of the terminal through hole 510 formed at the center of the cap plate 500. The thickness of the safety vent 530 may be, for example, about 0.05 mm to about 0.1 mm when the thickness of the cap plate is about 0.5 mm to about 1.0 mm.

In addition, the thickness of the portion in which the recess 531 of the safety vent 530 is formed may be 0.005 mm to 0.03 mm smaller than that.

This is to form the recess 531 in the safety vent 530, the safety vent 530 is more sensitive to the increase in the internal pressure to improve the safety of the lithium secondary battery 200.

That is, since the safety vent 530 has a cross-shaped recess 531, the breaking pressure of the safety vent 530 is lowered, thereby improving the safety of the secondary battery 200.

As described above, the lithium secondary battery 200 according to the embodiment of the present invention includes the recess 531 of the cross shape in the safety van 530, thereby providing the safety van 530 at a lower internal pressure. So as to be destroyed, the safety of the lithium secondary battery 200 can be improved.

As described above, according to the present invention, the present invention may provide a lithium secondary battery having improved safety of a secondary battery by having a safety vent that can be more easily broken when the internal pressure increases.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (5)

A wound electrode assembly having a first electrode plate, a second electrode plate, a separator interposed between the first electrode plate and the second electrode plate; A case having a space for accommodating the electrode assembly; And a cap plate coupled to the case to seal the cap plate, the cap plate including a safety vane having a predetermined recess, and an electrode terminal electrically connected to the electrode assembly. The method of claim 1, The main portion is a lithium secondary battery, characterized in that formed in the cross. The method of claim 1, The thickness of the safety vent is a lithium secondary battery, characterized in that 0.05mm to 0.1mm. The method of claim 1, The thickness of the portion where the recess is formed is a lithium secondary battery, characterized in that 0.005mm to 0.03mm. The method of claim 1, The cap plate has a terminal hole through which the electrode terminal is inserted and an electrolyte injection hole for injecting an electrolyte solution, The safety vent is a lithium secondary battery, characterized in that formed on the opposite side of the electrolyte injection opening on the basis of the terminal through.

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