KR20070069860A - Secondary battery - Google Patents

Abstract

Provided is a secondary battery, which includes a vent disposed at a controlled position on the wider surface of a can to facilitate discharge of the gases generated inside the battery. The secondary battery comprises: an electrode assembly including a unit cell(12) and electrode tabs drawn from the two different electrodes of the unit cell; a can for housing the electrode assembly; and a cap assembly coupled to the opened top of the can, wherein a vent(200) having an opening is formed on the wider surface(10a) of the can and at least a part of the opening of the vent is disposed over the portion of the wider surface of the can corresponding to the top of the unit cell.

Description

Secondary Battery {SECONDARY BATTERY}

1 is an exploded perspective view illustrating a secondary battery according to an embodiment of the present invention;

2 is a front view of a wide side of the can of the secondary battery shown in FIG. 1;

3 is a front view of a wide side of a can of a secondary battery according to another embodiment of the present invention;

4 is a stress distribution diagram of a wide side of a can generated by battery internal pressure.

Explanation of symbols on the main parts of the drawings

1: secondary battery 10: can

10a: wide side of the can 11: electrode assembly

12: battery unit 100: cap assembly

200, 200 ': vent opening

The present invention relates to a secondary battery, and more particularly, to a secondary battery in which gas generated inside a battery is smoothly discharged by adjusting a position of a vent formed on a wide side of a can.

In general, a secondary battery refers to a battery that can be charged and discharged, unlike a primary battery that cannot be charged, and is widely used in the field of advanced electronic devices such as a cellular phone, a notebook computer, a camcorder, and the like. In particular, lithium secondary batteries have an operating voltage of 3.6V, which is three times higher than nickel-cadmium batteries or nickel-hydrogen batteries, which are widely used as electronic equipment power sources, and are rapidly increasing in terms of high energy density per unit weight.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. Moreover, although lithium secondary batteries are manufactured in various shapes, typical shapes include cylindrical shape, square shape, and pouch type.

Among these, the rectangular secondary battery includes an electrode assembly, a can containing the electrode assembly, and a cap assembly coupled to the can.

The electrode assembly includes a battery part and an electrode tab. The battery part is wound around a positive electrode and a negative electrode and a separator interposed between these two electrodes to form a jelly roll, and the positive and negative electrode tabs are drawn out from the positive and negative electrodes of the battery part, respectively.

The can is a metal container having a substantially rectangular parallelepiped shape in a rectangular secondary battery, and is formed by a processing method such as deep drawing. It is therefore possible for the can itself to act as a terminal. As the material for forming the can, aluminum or aluminum alloy, which is a lightweight conductive metal, is preferable. The can becomes a container of the electrode assembly and the electrolyte solution, and the upper portion opened to insert the electrode assembly is sealed by the cap assembly.

The cap assembly includes a cap plate coupled to an upper portion of the can, an electrode terminal provided through a terminal hole, and a gasket for insulating the cap plate on an outer surface thereof, an insulating plate installed on a lower surface of the cap plate, It is provided on the bottom surface of the insulating plate and comprises a terminal plate that is energized with the electrode terminal. The negative electrode of the electrode assembly is electrically connected to the electrode terminal through the negative electrode tab and the terminal plate, and the positive electrode is electrically connected to the cap plate or the can through the positive electrode tab.

Meanwhile, a vent may be formed at one side of the cap plate, or a vent may be formed at a wide side of the can. Vents formed on the wide sides of the can (hereinafter, also referred to as 'side vents') are portions in which openings having grooves having a predetermined depth are formed. The vent opening breaks preferentially than other parts when the internal pressure of the battery increases due to overcharging, and thus releases the internal gas, thereby ensuring safety of the battery.

In designing the existing side vent, the shape and position of the vent and the thickness of the opening were determined in consideration of only the distribution of stress generated when the can is swelled by the pressure of the internal gas of the battery.

For example, since the greatest stress is applied to the corner of the wide side of the can during swelling, a side vent is formed at the corner of the can to make it sensitive to the increase in internal pressure. In this case, it is possible to have a relatively thick opening, thereby reducing the time and cost of the vent forming operation.

As another example, a side vent may be formed in the center between two upper corners of the four corners of the wide side of the can. The side vents formed at the corners of the can may cause cracks to spread to all parts of the cell upon breakage, and may break up to the welds of the capplates coupled to the top of the can, thus causing an electrode assembly and / or an electrode. Not only is the tab damaged, but there is a problem that reduces the reliability of the battery, to solve this problem.

However, in designing the side vents, it is very important that smooth discharge of internal gas can occur in addition to the above elements. Vent is also important to break pressure itself, but rather because the internal gas is smoothly discharged to ensure the stability of the battery is the original purpose.

However, in the existing side vents, the upper end of the opening is positioned below the upper end of the battery unit housed in the can or on the same reference line. Accordingly, even if the vent opening is opened due to the break pressure of the vent, the internal gas may not be discharged smoothly.

In particular, when the gas pressure inside the battery is gradually increased by the first reaction, the opening of the vent is broken and the internal gas is discharged, and afterwards, the secondary reaction in which a larger amount of gas is generated inside the battery is continued. In this case, the internal gas may not be discharged smoothly by the secondary reaction, and the battery may explode.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and an object thereof is to smoothly discharge gas generated inside a battery by adjusting a position of a vent formed on a wide side of a can.

In order to achieve this object, the secondary battery according to the present invention,

An electrode assembly having a battery unit and electrode tabs respectively drawn from the two electrodes of the battery unit; A can containing the electrode assembly; And a cap assembly coupled with the open top of the can,

A vent is formed in the wide side of the can with a groove formed at a predetermined depth, and at least some of the opening of the vent is positioned above the portion corresponding to the upper end of the battery unit among the wide sides of the can. It is done.

In this case, one side of the opening of the vent may be located above the portion corresponding to the upper end of the battery unit while being parallel to the upper side of the wide side of the can.

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

1 is an exploded perspective view illustrating a rechargeable battery according to an exemplary embodiment of the present invention.

Referring to the drawings, the secondary battery includes an electrode assembly 11, a can 10 accommodating the electrode assembly 11, and a cap assembly 100 coupled to the can 10.

The electrode assembly 11 includes a battery part 12 for generating electricity and electrode tabs 16 and 17 coupled to the battery part 12 to draw electricity to the outside. The battery unit 12 usually forms the positive electrode 13 and the negative electrode 15 in a wide plate shape in order to increase the capacitance, and then interposes the separator 14 between the positive electrode 13 and the negative electrode 15 to insulate them from each other. It is then laminated, rolled up into a vortex to form a so-called 'Jelly Roll'. The negative electrode 15 and the positive electrode 13 may be formed by coating carbon as the negative electrode active material and lithium cobalt as the positive electrode active material, respectively, on a current collector made of copper and aluminum foil. The separator 14 is made of polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene. Separator 14 is formed to be wider than the positive electrode 13 and the negative electrode 15 is advantageous to prevent short circuit between the electrode plates. In the battery unit 12, positive and negative electrode tabs 16 and 17 connected to each electrode are drawn out. The insulating tape 18 is wound around the positive and negative electrode tabs 16 and 17 to prevent a short circuit between the electrode plates 13 and 15 at the boundary portion drawn out of the battery unit 12.

The can 10 is a metal container having a substantially rectangular parallelepiped shape in the rectangular secondary battery as shown, and formed by a processing method such as deep drawing. It is therefore possible for the can itself to act as a terminal. As the material for forming the can, aluminum or aluminum alloy, which is a lightweight conductive metal, is preferable. The can 10 becomes a container of the electrode assembly 11 and the electrolyte solution, and the upper part opened so that the electrode assembly 11 is introduced is sealed by the cap assembly 100. A vent 200 is formed on the wide side of the can, which will be described later.

The cap assembly 100 includes a cap plate 110, an electrode terminal 130, an insulating plate 140, and a terminal plate 150. The cap plate 110 has a terminal through hole 111 formed therein, and the electrode terminal 130 penetrates through the terminal through hole 111 with the gasket 120 positioned on the outer surface thereof to insulate the cap plate 110. Is installed. An insulating plate 140 is provided on the lower surface of the cap plate 110, and a terminal plate 150 is provided on the lower surface of the insulating plate 140. The lower end of the electrode terminal 130 is coupled to the terminal plate 150.

The negative electrode 15 of the electrode assembly 11 is electrically connected to the electrode terminal 130 through the negative electrode tab 17 and the terminal plate 150. In the case of the positive electrode 13 of the electrode assembly 11, the positive electrode tab 16 is welded to the cap plate 110 or the can 10. An insulating case 190 may be further installed below the terminal plate 150. On the other hand, the battery may be designed by changing the polarity.

An electrolyte injection hole 112 for injecting an electrolyte into the can 10 is formed at one side of the cap plate 110, and a sealing unit 160 for sealing the electrolyte injection hole 112 after electrolyte injection is provided. Is formed.

Vent 200 formed on the wide side of the can in more detail as follows.

Referring to FIG. 2, in the rechargeable battery according to the exemplary embodiment, a vent having a groove 200 is formed at a predetermined depth in a wide side surface 10a of the can, and a vent having an opening 200 is formed. At least a portion of the can is positioned above the portion corresponding to the upper end of the battery unit 12 of the wide side 10a of the can.

Vent is a part in which the opening 200 having a predetermined depth is formed, and when the pressure due to the internal gas of the battery increases due to overcharging, etc., the vent breaks preferentially than other parts to release the internal gas, thereby ensuring the safety of the battery. Do it.

The opening of the vent may have various shapes at various positions in consideration of the stress distribution inside the battery and the height of the upper end of the battery during swelling.

First, the position of the opening of the vent is considered in consideration of the height of the upper end of the battery unit.

The consideration of the height of the top of the battery compartment means that the gas can be smoothly discharged when the opening of the vent is opened by the internal gas pressure during swelling. For this purpose, at least a part of the opening of the vent is located above the top of the battery compartment. It means that it needs to be located.

2 and 3, one side (upper side) of the openings 200, 200 ′ is parallel to the upper side of the wide side 10 a of the can, and the top of the battery unit 12 of the wide side 10 a of the can. It is located above the part corresponding to. Therefore, when the openings 200 and 200 ′ of the vent are opened by the internal gas pressure, the discharge of the gas is not disturbed by the battery unit 12, and thus the gas may be smoothly discharged.

The upper side 210 of the vent opening 200 is disposed in parallel to the upper side of the wide side 10a of the can. The upper side 210 of the vent is formed in a straight line rather than the curved opening 200. It is easy to break. In addition, since the upper side 210 formed in a straight line at the center of the can is not inclined and disposed in parallel to the upper side of the can, the stress caused by the battery pressure gas acts uniformly on the opening 200 of the vent, so that the break pressure design of the vent is achieved. It becomes easy.

On the other hand, when looking at the stress distribution of the wide side 10a of the can swelled by the internal gas of the battery (where the can has a long side of 48.7 mm and a short side of 33.8 mm), as shown in FIG. It can be seen that the stress increases in the order of the side portion 21, the planar portion 22, the first corner portion 23, and the second corner portion 24. That is, when the can is swelled by the pressure of the internal gas, the greatest stress is generated in the corner portions 23 and 24.

The upper side of the vent opening 200 is preferably 2.0 to 3.0 mm apart from the upper side of the wide side 10a of the can. The upper end of the battery part 12 is normally spaced about 3.0 mm from the upper side of the wide side surface 10a of the can. Therefore, when the separation distance is greater than 3.0mm, even if the opening 200 of the vent is opened by the internal gas pressure, the discharge of the gas is prevented by the battery unit 12, the gas can not be smoothly discharged. On the other hand, when smaller than 2.0 mm, as shown in FIG. 4, since the break of the upper side of the said vent is not easy adjacent to the edge 21 of the can which is the weakest in stress, the battery stability is impaired.

Next, the position and shape of the opening of the vent are considered in consideration of the stress distribution inside the battery during swelling.

2 and 3, the openings 200 and 200 ′ of the vents have a polygonal shape with one side open, and the open portion is positioned toward the center of the wide side 10a of the can.

Referring to FIG. 3, since the greatest stress is applied to the corners of the wide side 10a of the can during swelling, the side vent 200 ′ is applied to at least one of the two upper corners of the four corners of the can. To react sensitively to the increase in internal pressure. In this case, since it may have a relatively thick opening 200 ', it is possible to reduce the time and cost of the vent forming operation.

-형)을 띄고 있다. 이때, 상기 벤트는 캔의 넓은 측면(10a)의 네 귀퉁이부분 가운데 상부의 두 귀퉁이부분 사이 중앙에 위치하여 있다. 이 경우, 내압에 의해 벤트의 개구부(200) 파단시 캔의 과도한 파손을 막아 전극조립체 및/또는 전극탭의 손상을 방지할 수 있다.Meanwhile, referring to FIG. 2, the opening 200 of the vent has a rectangular shape (one side of which is open)

-Type). At this time, the vent is located at the center between the two corners of the top of the four corners of the wide side 10a of the can. In this case, excessive breakage of the can at the time of breaking the opening 200 of the vent may be prevented by internal pressure to prevent damage to the electrode assembly and / or the electrode tab.

In the secondary battery according to the present invention, at least a part of the opening of the vent formed on the wide side of the can is positioned above the portion corresponding to the upper end of the battery unit, so that the gas generated inside the battery can be discharged smoothly. have.

Although the present invention has been described with reference to the illustrated embodiments, it is merely exemplary, and the present invention may encompass various modifications and equivalent other embodiments that can be made by those skilled in the art. Will understand.

Claims (7)

An electrode assembly having a battery unit and electrode tabs respectively drawn from the two electrodes of the battery unit; A can containing the electrode assembly; In the secondary battery comprising a cap assembly coupled to the open top of the can, A vent is formed in the wide side of the can with a groove formed at a predetermined depth, and at least some of the opening of the vent is positioned above the portion corresponding to the upper end of the battery unit among the wide sides of the can. Secondary battery. The method of claim 1, One side of the vent opening is parallel to the upper side of the wide side of the can and the secondary battery, characterized in that located above the portion corresponding to the top of the battery unit. The method of claim 2, The one side of the opening of the vent is a secondary battery, characterized in that spaced 2.0 to 3.0mm from the upper side of the wide side of the can. The method according to claim 1 or 2, The opening of the vent has a polygonal shape with one side open, and the open portion is positioned to face the center of the wide side of the can. The method of claim 4, wherein The opening of the vent has a rectangular shape with one side open (

-) Secondary battery characterized in that. The method of claim 4, wherein The vent is a secondary battery, characterized in that located in the center between the two corners of the top of the four corners of the wide side of the can. The method of claim 4, wherein The vent is a secondary battery, characterized in that located in at least one of the two corners of the upper corner of the four corners of the wide side of the can.

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