KR100614385B1 - Cap Assembly and Lithium Secondary Battery with the same - Google Patents

Abstract

The present invention relates to a cap assembly and a lithium secondary battery having the same, which is stable against an external impact but can be easily broken by a constant low pressure against an internal pressure, and an improved cap assembly and a lithium secondary having the same It relates to a battery.

Secondary battery, fundus hole, stopper

Description

Cap assembly and Lithium secondary battery having the same {Cap Assembly and Lithium Secondary Battery with the same}

1A and 1B illustrate a conventional cap assembly.

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

3 is a cross-sectional view of the cap plate of the lithium secondary battery according to the first embodiment of the present invention.

4 is a cross-sectional view of the cap plate of the lithium secondary battery according to the second embodiment of the present invention.

5 is a cross-sectional view of a cap plate of a lithium secondary battery according to a third embodiment of the present invention.

6 is a cross-sectional view of the cap plate of the lithium secondary battery according to the fourth embodiment of the present invention.

7 is a cross-sectional view of the cap plate of the lithium secondary battery according to the fifth embodiment of the present invention.

<Brief description of symbols for the main parts of the drawings>

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 ... Secondary electrode tab 330 ... Separator

340 ... insulating tape 400 ... cap assembly

410 cap plate 411 terminal hole

412 Electrolyte inlet 413

415 ... plug 420 ... terminal electrode

430 Gasket 440 Insulation Plate

450 ... terminal plate 460 ... insulated case

462 ... electrolyte injection hole 550, 650, 750, 850, 950 ... safety vent hole

The present invention relates to a cap assembly and a lithium secondary battery having the same, which is stable against an external impact but can be easily broken by a constant low pressure against an internal pressure, and an improved cap assembly and a lithium secondary having the same It relates to a battery.

In general, a secondary battery refers to a battery that can be charged and discharged and has a small size and a large capacity, unlike a primary battery that cannot be charged. Typically, a secondary battery is a nickel-cadmium (Ni-Cd) battery and a nickel hydrogen (Ni-MH) battery. Batteries, lithium (Li) batteries and lithium ion (Li-ion) batteries are used. Recently developed lithium ion secondary batteries are widely used in the field of advanced electronic devices such as cellular phones, notebook computers.

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

Such lithium ion secondary batteries use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. A lithium ion secondary battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to the type of electrolyte. 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.

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 move only lithium ions (Li-ion). The electrode assembly is formed of a wound electrode, a lithium ion secondary battery case accommodating the electrode assembly, and an electrolyte solution injected into the lithium secondary battery case to enable movement of lithium ions.

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 and the negative electrode tab is connected to the negative electrode plate and the separator is wound to manufacture an electrode assembly. The electrode assembly is accommodated in the lithium secondary battery case, the cap assembly is assembled on the upper case for the lithium secondary battery to prevent the separation of the electrode assembly. The electrolyte is injected into and sealed in the case for the lithium ion secondary battery assembled with the cap assembly to complete the battery.

In general, when the battery is normally charged, reactions such as melting of an organic solvent, pyrolysis of the SEI film of the negative electrode, reaction of the negative electrode active material and the electrolyte, reaction of the oxygen and the electrolyte decomposed in the positive electrode active material, and decomposition of lithium are sequentially performed. Occurs. However, when the battery is overcharged, the above reactions proceed simultaneously to generate an exothermic reaction, whereby the gas is unstable at the same time as the expansion due to the ejected gas. The generation of gas continues until the cell ruptures, so the gas must be released to the outside at a predetermined pressure.

1A and 1B show a view for explaining a conventional cap assembly.

1A and 1B, the cap assembly includes a cap plate 100 having a safety vent 110 formed thereon for releasing the gas generated by the simultaneous multiplication. The safety vent 110 is broken when the internal pressure of the battery rises, so that the internal gas and the like are discharged to the outside, thereby improving the safety of the battery.

However, the safety vent 110 is formed very thin compared to the cap plate 100, the material is formed of a thin metal sheet, such as aluminum or aluminum alloy. Therefore, when the battery is physically impacted from the outside due to a drop, etc., a problem occurs in which the crack occurs in the safety vent 110 and the electrolyte is leaked inside the battery, thereby preventing the safety and reliability of the battery. There is this.

The present invention relates to a cap assembly and a lithium secondary battery having the same, which is stable against external shocks but can be broken by a constant pressure with respect to an internal pressure, and a cap assembly and an improved lithium secondary battery having the same. The purpose is to provide.

In order to achieve the above object, the cap assembly of the present invention includes at least a cap plate having a safety vane hole formed therein, and the safety vane hole is formed of a flexible resin broken by a predetermined internal pressure and is coupled to the cap plate outer surface. It is characterized in that it is closed with a stopper having a jaw.

In addition, the lithium secondary battery of the present invention is a wound electrode assembly having a first electrode plate and a second electrode plate and a separator interposed between the first electrode plate and the second electrode plate, and for receiving the electrode assembly Cap plate provided with a case having a space and at least a safety vent hole is formed of a flexible resin that breaks at a certain internal pressure, the shape is any one of ∩, U, H, and a stopper for closing the safety vent hole It characterized in that it comprises a cap assembly having a.

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

2 is an exploded perspective view of a rechargeable lithium battery according to one embodiment of the present invention.

Referring to FIG. 2, the lithium secondary battery 200 according to the embodiment of the present invention includes a lithium secondary battery case 210, an electrode assembly 300 accommodated inside the lithium secondary battery case 210, and the It includes a cap assembly 400 coupled to the upper portion of the lithium secondary battery case 210.

The lithium secondary battery case 210 is a metal container having an open top shape, and generally, aluminum or an aluminum alloy is used that is light and easy to cope with corrosion. It is also possible to itself serve as a terminal.

The electrode assembly 300 is interposed between the first electrode plate 310, the second electrode plate 320, and the first electrode plate 310 and the second electrode plate 320 to insulate them from each other. 330 is included.

The electrode assembly 300 has a first electrode plate and a second electrode plate 310, 320, and the separator 330 is composed of a single strip, each of the first electrode plate 310, the separator 330, The second electrode plate 320 and the separator 330 are arranged in this order, and are wound in a jelly-roll type.

The first electrode tab 315 is welded to the first electrode plate 310, and the second electrode tab 325 is welded to the second electrode plate 320, and the first electrode tab 315 and the second electrode tab ( One end of the 325 protrudes above the electrode assembly 300. The first electrode plate 310 and the second electrode plate 320 are wrapped with an insulating tape 340 to prevent a short circuit between the positive electrode plates. The first electrode plate 310 and the second electrode plate 320 may serve as a positive electrode plate or a negative electrode plate.

For example, the first electrode plate 310, which is used as a negative electrode plate, is coated with a negative electrode current collector made of a conductive metal plate, such as a copper foil, and a slurry composed mainly of a carbon material on both surfaces thereof.

For example, the second electrode plate 320, which is used as the positive electrode plate, is coated with a positive electrode current collector made of a metal thin plate having excellent conductivity, such as aluminum foil, and a slurry containing lithium-based oxide as a main component on both surfaces thereof.

The separator 330 is made of polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene. The separator 330 may be formed to have a wider width than the first electrode plate 310 and the second electrode plate 320 to prevent short circuit between the electrode plates 310 and 320.

The cap assembly 400 is provided with a flat cap plate 410 having a size and shape corresponding to the opening of the lithium 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 sealed by the bowl 413.

The other side of the electrolyte injection hole 412 is provided with a safety vent hole (not shown) for improving the safety of the battery by releasing the gas inside the battery when a predetermined breakdown voltage of the lithium secondary battery 200 is generated. The safety vent hole is closed with a stopper 415 formed of a flexible resin that breaks at a predetermined internal pressure. The stopper 415 closing the safety vent hole forms a jaw coupled with the outer surface of the cap plate 410. have. The stopper 415 may be fixed to the cap plate 410 by an adhesive. The stopper 415 is formed to be thinner than the thickness of the cap plate 410 to release the gas when the internal pressure increases above a predetermined pressure.

An electrode terminal 420, for example, a negative electrode terminal, may be inserted into the terminal through hole 411 of the cap plate 410. 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 a lower surface of the cap plate 410 near the terminal plate hole 411 of the cap plate 410. The terminal plate 450 is installed on the lower surface of the insulating plate 440.

The electrode terminal 420 is inserted through the terminal through hole 411 while the gasket 430 surrounds the outer circumferential surface. The lower surface portion of the electrode terminal 420 is electrically connected to the terminal plate 450 in a state where the insulating plate 440 is opened.

An insulating case 460 is installed on the upper surface of the electrode assembly 300 to electrically insulate the electrode assembly 300 from the cap assembly 400, and at the same time to cover the upper end of the electrode assembly 300. It is. 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.

3 is a cross-sectional view of a cap plate of a lithium secondary battery according to a first embodiment of the present invention. 4 is a cross-sectional view of a cap plate of a lithium secondary battery according to a second embodiment of the present invention.

Referring to FIG. 3, the cap plate 410 for a rechargeable lithium battery according to the first embodiment of the present invention includes a terminal through hole 411, an electrolyte injection hole 412, a safety vent hole 470, and the safety vent hole 470. 4), a cap plate 512 for a rechargeable lithium battery according to a second embodiment of the present invention is provided with a terminal through hole 511 and an electrolyte injection hole 512. It is formed with a safety vent hole 570 and a stopper 515 finishing the same.

As shown in FIGS. 3 and 4, the stoppers 415 and 515 may be formed of a flexible resin having grooves formed in a lower portion of the stopper hole 570 in a ∩ shape, and in an upper side in a U shape. The groove may be formed of a flexible resin material having a groove. The stopper may preferably be formed of rubber.

The flexible resin stoppers 415 and 515 have greater flexibility and strength than safety vanes formed of metal thin plates such as aluminum or aluminum alloys, and thus cracks are easily generated when external pressure such as drops occur. To improve the reliability of the battery.

In addition, the stoppers 415 and 515 have grooves formed in the inner or outer direction of the cap plates 410 and 510 so that the thickness of the stoppers 410 and 510 is smaller than that of the cap plates 410 and 510 so that the inside of the caps 415 and 515 is thinner. When the pressure of more than a certain, it can be easily broken. The stoppers 415 and 515 may be fixed on the cap plates 410 and 510 with an adhesive.

5 is a cross-sectional view of a cap plate of a lithium secondary battery according to a third embodiment of the present invention.

Referring to FIG. 5, a stopper 615 closing the safety vent hole 670 provided in the cap plate 610 for a lithium secondary battery according to the third embodiment of the present invention blocks a safety vent hole 670. This H-shaped flexible resin is formed, and preferably rubber. The stopper 615 is a groove formed in the upper and lower direction, and when the internal pressure of the battery is increased, the portion to be broken in order to eject the gas is located in the middle of the thickness direction of the cap plate 610.

The stopper 615 formed of the flexible resin or the rubber material is not easily broken by external impact due to the characteristics of the material, but the grooves are formed in the upper and lower directions so that the stopper 615 is larger than the thickness of the cap plate 610. When the internal pressure becomes thinner than a certain thickness, it is broken and the safety of the battery can be improved. The stopper 615 may be fixed on the cap plate 610 with an adhesive.

6 is a cross-sectional view of a cap plate of a lithium secondary battery according to a fourth embodiment of the present invention. 7 is a cross-sectional view of a cap plate of a lithium secondary battery according to a fifth embodiment of the present invention.

6 and 7, the stoppers 715 and 815 closing the safety vent holes 770 and 870 formed in the cap plates 710 and 810 for the rechargeable lithium battery according to the fourth and fifth embodiments of the present invention are flexible resins. It may be formed of, and preferably formed of rubber. Notches 740 and 840 are formed above or below the stoppers 715 and 815. The notches 740 and 840 allow the stoppers 715 and 815 to break along the notches 740 and 840 when the internal pressure of the battery increases, and the stoppers 715 and 815 quickly break when the internal pressure increases. Allow gas to be released.

The stoppers 715 and 815 may have a U, H, and H shape, and the notches 740 and 840 may be formed on both upper and lower sides thereof. In addition, the notches 740 and 840 may be formed in a V or U shape.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary knowledge in the technical field to which the present invention belongs 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.

As described above, according to the present invention, it is possible to provide a cap assembly and a lithium secondary battery having improved reliability and safety, which are stable against external impact but can be easily broken by a constant low pressure against internal pressure.

Claims (15)

A cap assembly having a cap plate with at least a safety vent hole formed therein, The cap plate has a stopper for closing the safety vent hole, the stopper is formed of a flexible resin that is broken at a predetermined internal pressure and a cap assembly, characterized in that forming a jaw coupled with the outer surface of the cap plate. delete The method of claim 1, Cap assembly, characterized in that the stopper is formed of rubber. The method of claim 1, The stopper is a cap assembly, characterized in that the groove blocking portion is formed in the lower portion in the shape of the block blocking the safety vent hole. The method of claim 1, The stopper is a cap assembly, characterized in that the portion blocking the safety vent hole is formed in a U-shaped upper portion. The method of claim 3, wherein  Cap assembly, characterized in that the portion blocking the safety vent hole of the stopper is formed in an H shape. The method of claim 1, The cap assembly is characterized in that the notch is formed on the outside. The method of claim 1, The cap assembly is characterized in that the notch is formed on the inside. The method according to claim 7 or 8, The notch is a cap assembly, characterized in that formed in a V or U shape. The method of claim 1, And the cap is secured by an adhesive. 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; At least a safety vent hole is formed, the cap assembly is formed of a flexible resin that breaks at a certain internal pressure, the shape of any one of ∩, U, H and having a cap plate having a cap for closing the safety vent hole Lithium secondary battery comprising a. The method of claim 11, The stopper is a lithium secondary battery, characterized in that formed of rubber. delete The method of claim 11, The stopper is a lithium secondary battery, characterized in that the notch is formed on the outside or inside. The method of claim 11, The stopper is a lithium secondary battery, characterized in that fixed by an adhesive.

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