Battery pack

A battery case including: first case body having a main wall and opposing side walls; a second case body including a second main wall and opposing side walls. The first and second side walls include coupling parts to be coupled together when the first and second case bodies are pressed together to form a space to receive a bare cell. The battery case can also include clips to couple the first and second side walls.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Application No. 2007-49248, filed May 21, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to a battery pack, and more particularly, to a battery pack in which a coupling part of a case that is formed to enclose a bare cell is closely contacted to prevent a molding being inferior due to a molding material leaking from the coupling part of the case during the molding using resin or hot melt.

2. Description of the Related Art

Recently, compact and portable electronic/electric appliances, such as, cellular phones, lap-top computers, camcorders, and so on, have been actively developed and produced, and require battery packs for portable operations. In consideration of economical concerns, a battery pack generally includes a secondary battery that is rechargeable, such as, a nickel-cadmium (Ni—Cd) battery, a nickel-hydrogen (Ni-MH) battery, and a lithium (Li) battery.

Battery packs including an Li secondary battery are widely used for the portable electronic/electric appliances. The Li secondary battery is used because an Li secondary battery has an operating voltage three times larger than that of the Ni—Cd battery or the Ni-MH battery, and an energy density per unit weight larger than that of the Ni—Cd battery or the Ni-MH battery. An Li secondary battery may be classified as an Li ion battery using a liquid electrolyte, and a Li polymer battery using polymer electrolyte, according to the type of electrolyte used. The Li secondary battery can also be classified according to shape, for example, as a cylindrical Li battery, a rectangular Li battery, and a pouch-type Li battery.

A battery pack using an Li secondary battery includes a bare cell and a protecting circuit board electrically connected to the bare cell, to prevent the bare cell from being excessively discharged and overcharged. In order to attach the bare cell and the protecting circuit board, a molding process is usually performed. The molding process fills a space formed between the bare cell and the protecting circuit board using molding material such as, a resin, a hot melt, and so on. Here, the bare cell is fabricated such that in an electrode assembly, including a positive electrode plate and a negative electrode plate, electrode taps are connected to electrode collectors, which are coated with an electrode active material, and a separator disposed between the positive electrode plate and the negative electrode plate. The bare cell is disposed in an open-topped can. The opened top of the can is sealed by a cap assembly.

When strength of the battery pack is reinforced to protect the bare cell from exterior impacts by enclosing the outer side of the bare cell, the case is physically coupled to improve the reliability of the bare cell. However, the case is not completely coupled at coupling parts, so that the molding material leaks from the coupling parts and causes an inferiority molding of the battery pack.

SUMMARY OF THE INVENTION

Aspects of the present invention are directed to a battery case of a battery pack, in which side walls of the case interlock with each other, in order to improve molding of the battery pack.

Aspects of the present invention provide a battery case for a battery pack. The battery pack can comprise: a bare cell; a protecting circuit board electrically connected to the bare cell; and a case to enclose the bare cell and including coupling parts.

Aspects of the present invention provide a battery case can comprise first side walls, second side walls, and tabs extending from the first side walls. The tabs are folded over the second side walls to couple the first and second side walls.

Aspects of the present invention provide a battery case including clips to couple first and second side walls of the case.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below in order to explain the aspects of the present invention by referring to the figures. When some part is described as being “connected to” other part, this refers to a “direct connection” and an “electrical indirect connection” including component(s) therebetween.

FIG. 1is an exploded perspective view illustrating a bare cell101, according to an exemplary embodiment of the present invention. Referring toFIG. 1, the bare cell101includes an electrode assembly100, a can200having an opened upper end, to accommodate an electrolyte (not shown), so that Li ions can move within the electrode assembly100, and a cap assembly300to seal the can200. The electrode assembly100includes a positive electrode plate120having a positive electrode tap150, which is electrically connected to a positive electrode collector (not shown) coated with positive electrode active material (not shown), a negative electrode plate110having a negative electrode tap140which is electrically connected to a negative electrode collector (not shown) coated with negative electrode active material (not shown), and a separator130disposed between the positive electrode plate120and the negative electrode plate110.

The positive electrode active material may include Li-containing transition metal oxides or Li chalcogenide compounds. For example, the active material can be LiCoO2, LiNiO2, LiMnO2, LiMn2O4, or LiNi1-x-yCoxMyO2 (wherein 0≦x≦1, 0≦y≦1, 0≦x+y≦1, and M is a metal such as Al, Sr, Mg, La, and so on). The negative electrode active material may include carbon materials, such as, crystalline carbon, amorphous carbon, a carbon complex, carbon fiber, and so on, a lithium metal, or a lithium alloy.

The positive electrode collector or the negative electrode collector may be formed of a material that is selected from a group consisting of a stainless steel, nickel, copper, aluminum, and alloys thereof. Preferably, the positive electrode collector may be formed of the aluminum or an aluminum alloy, and the negative electrode collector may be formed of the copper or a copper alloy, thereby maximizing efficiency. However, the collectors are not so limited.

The separator130is disposed between the positive electrode plate120and the negative electrode plate110so as to prevent electrical short circuit and to enable movement of a Li ion. The separator130may be formed of a polyolefin-based polymer layer such as polyethylene (PE) and polypropylene (PP), or a multi-layer thereof.

The can200, as illustrated in the drawing, may be formed of a rectangular shape, and may be alternately formed of cylindrical or pouch shape. The can200may be fabricated from a metal material. Preferably, the can200may be fabricated from a light-weight and flexible metal material, such as, aluminum, an aluminum alloy, a stainless steel, or the like, which allows the can200to function as a terminal. The can200forms an interior cavity to hold the electrode assembly100. As shown, the can200is a solid shape that does not deform during manufacture. However, aspects can use pouch-type containers that deform due to their having soft sides.

The cap assembly300is coupled to the upper opening of the can200and includes a cap plate350, an insulation plate340, a terminal plate330, an insulation case320, and an electrode terminal310. The cap plate350is a metal plate having a size and a shape corresponding to the upper opening of the can200. The cap plate350includes a terminal hole of a predetermined size, an electrolyte injection hole, and a safety vent (not shown). The safety vent may be formed at any region where it does not interfere with the terminal hole and the electrolyte injection hole.

The electrode terminal310is inserted into the terminal hole and is connected to the terminal plate330. In this case, in order to insulate the cap plate350from the electrode terminal310, a gasket360, formed of an insulating rubber or a non-conductive material, is disposed to insulate the electrode terminal310.

The electrolyte, if a liquid electrolyte, is injected through electrolyte injection hole into the can200, in which the electrode assembly100is accommodated, so as to smoothly move Li ions during the discharge or the recharge of the bare cell101. The electrolyte is injected through the electrolyte injection hole, after sealing the can200using the cap assembly300, and the electrolyte injection hole is sealed by an electrolyte injection hole stopper370, so as to seal the can200. However, it is understood that, if a solid electrolyte is used, no electrolyte injection hole need be used, and the electrolyte can be used in addition to or instead of the separator130.

The insulation plate340and the terminal plate330are sequentially disposed under the cap plate350. The terminal plate330is electrically connected to the electrode terminal310and the negative electrode tap140, so that the electrode terminal310is electrically connected to the negative electrode tap140. The insulation plate340is disposed between the cap plate350and the terminal plate330, to insulate the cap plate350from the terminal plate330.

The insulation case320may be formed of an insulating polymer resin, such as, polypropylene (PP), polyphenylene sulfide (PPS), polyethersulfone (PES), modified polyphenylene oxide (PPO), or the like. The insulation case320is disposed on the upper opening of the can200, to cover the upper side of the electrode assembly100and to fix the positive electrode tap150and the negative electrode tap140of the electrode assembly100. The insulation case320may include a support frame formed in the periphery of thereof, to safely position the terminal plate330and the insulation plate340.

Although not depicted, the bare cell101, including the electrode assembly100, the can200, and the cap plate300, is connected to the protecting circuit board (not shown), such that a discharge and the recharge of the bare cell is controlled. The protecting circuit board is configured such that a plurality of electric components are mounted on a printed circuit board (PCB), in which interconnection patterns are formed, and is electrically connected to the bare cell101, via a lead plate. Here, a secondary protecting device, such as, a positive temperature coefficient (PTC), a thermal fuse, a bimetal, or a thermal braker, may be disposed between and be electrically connected to the bare cell101and the protecting circuit board, to control the current in the bare cell according to an ambient temperature.

FIGS. 2A to 2Care perspective views illustrating battery cases500A-500C, of a battery pack, according to exemplary embodiments of the present invention. Referring toFIG. 2A, the case500A is to house the bare cell101, and thereby form a battery pack. The case500A includes a first case body510A, including first side walls517A, which include first coupling parts515A; and a second case body520A, including second side walls527A, which include second coupling parts525A. The case500A also includes first and second main walls511and521, disposed between the first and second side walls517A and527A, and a bottom wall523disposed between the first and second case bodies510A and520A. The case500A may be formed of material that is strong enough to reinforce the strength of the battery pack. The case500A may be formed of a stainless steel, such as a steel use stainless (SUS), in order to ensure a light weight battery pack and/or for ease of manufacture.

The first case body510A and the second case body520A contact longitudinal sides of the bare cell101, when the bare cell101is inserted therein. The first and second coupling parts515A and525A are joined together, at coupling regions A of the case500A. The coupling regions A are positioned adjacent to narrow sides of the bare cell101. The first and second case bodies510A and520A are each bent toward one another, to join the first and second coupling parts515A and525A, such that a molding material (such as a resin or hot melt) injected into the case500A cannot pass between the first and second coupling parts515A and525A. The first and second coupling parts515A and525A are shown to be bent into interlocking semi-circular shapes. The first and second coupling parts515A and525A, and/or the first and second side walls517A and527A, can be elastically deformed during the coupling, but generally return to their originally shape after the coupling is completed, to maintain an interlocking relationship.

FIG. 2Billustrates a case500B to house the bare cell101. The case500B includes a first case body510B, including first side walls517B, which include first coupling parts515B; and a second case body520B, including second side walls527B, which include second coupling parts525B. The case500B is similar to the case500A, except for the shapes of the first and second coupling parts515B and525B. The first and second coupling parts515B and525B are shown to be bent into corresponding semi-rectangular shapes. The shapes of the first and second coupling parts510B and525B prevent a molding material (such as resin or hot melt), injected into the case500B, from passing between the first and second coupling parts515B and525B and exiting the case500B. The first and second coupling parts515B and525B, and/or the first and second side walls517B and527B, can be elastically deformed during the coupling, but generally return to their originally shape after the coupling is completed, to maintain an interlocking relationship.

FIG. 2Cillustrates a case500C to house the bare cell101. The case500C includes a first case body510C including first side walls517C, which include first coupling parts515C; and a second case body520C including second side walls527C, which include second coupling parts525C. The case500C is similar to the case500A, except for the shapes of the first and second coupling parts515C and525C. The first and second coupling parts515C and525C are shown to be bent into corresponding sinusoidal or wave shapes. The shapes of the first and second coupling parts510C and525C prevent a molding material (such as resin or hot melt), injected into the case500C, from passing between the first and second coupling parts510C and515C and exiting the case500C. The first and second coupling parts515C and525C, and/or the first and second side walls517C and527C, can be elastically deformed during the coupling, but generally return to their originally shape after the coupling is completed to maintain an interlocking relationship.

The first and second coupling parts515A-C and525A-C can be bent into any number of shapes, or other interlocking protrusions and depressions, so long as a molding or resin material is prevented from exiting the respective cases500A-C there through. Further, the parts515A-C and515A-C can be corrugated, in that they have multiple interlocking grooves and ridges. The second coupling parts525A-C can contact the bare cell101, or may be spaced apart from the bare cell101.

According to various embodiments, the first and second coupling parts515A-C and525A-C may be positioned at the longitudinal sides of the bare cell101(rather than the narrow sides). In other exemplary embodiments, the cases500A-C may be formed as an integrated body.

FIG. 3Ais an exploded perspective view illustrating a case502of a battery pack, according to another exemplary embodiment of the present invention, andFIG. 3Bis an exploded perspective view illustrating the case502before the case502is assembled. Referring toFIGS. 3A and 3B, the case502includes a first case body550, including first side walls555, and a second case body560, including second side walls565. The first side walls555include tabs530. The first and second case bodies550and560are coupled together by overlapping the first and second side walls555and565, at coupling regions B, and folding the tabs530over the second side walls565. The first case body550contacts one side of the bare cell101, and the second case body560contacts an opposite side of the bare cell101.

The case502can be made of any material having strength sufficient to reinforce the bare cell101. For example, the case502can be made of a stainless steel, such as a steel use stainless (SUS).

The bare cell101(not shown) is inserted between the first case body550and the second case body560to form the battery pack. The first case body550and the second case body560contact both longitudinal sides of the bare cell101, and the first and second side walls555and565are positioned at the narrow sides of the bare cell101. The case502may be formed as an integrated body. The case502may be configured such that the first and second side walls555and565are positioned at the longitudinal sides of the bare cell101.

The tabs530of the first coupling part555are bent toward the second coupling part565, such that the first case body550closely contacts the second case body560. The length of the tabs530can influence the position of the bare cell101in the case502and the strength of the coupling regions B. Therefore, the length of the tabs530generally ranges from about 5% to 10% of the length of the coupling regions B.

According to various embodiments, the second side walls565can be positioned inside of the first side walls555, i.e. closer to the bare cell101, and the tab530can be folded toward the bare cell101. However, when the tab530is bent toward the bare cell101, the tab530may contact and/or damage the bare cell101, due to swelling that occurs during the discharge and the recharge of the bare cell101. Thus, as illustrated inFIGS. 3A and 3B, the first side walls555are generally positioned nearer to the bare cell101than the second side walls565, and the tab530is bent away from the bare cell. Therefore, the tab530is prevented from contacting the bare cell.

According to various embodiments, the second coupling part565may also optionally have tabs530(not shown). However, when both of the first and second side walls555and565have tabs530, a thickness of the battery pack may be increased, without significantly improving the coupling of the first and second case bodies550and560.

FIG. 4Ais a perspective view illustrating a case504of a battery pack, according to still another exemplary embodiment of the present invention, andFIG. 4Bis an exploded perspective view illustrating the case504. Referring toFIGS. 4A and 4B, the case504includes a first case body570including first side walls575, a second case body580including second side walls585, and clips540to couple the first side walls575to the second side walls585at coupling regions C. The case504is similar to the case502, except that the case504lacks the tabs540. Here, although the case500including the first case body550and the second case body560is made of any material with strength sufficient to reinforce the battery pack, preferably the case504is made of a stainless steel, such as a steel use stainless (SUS), for weigh reduction and easy fabrication of the battery pack.

The bare cell101(not show) is inserted into the case504. The first case body570and the second case body580contact both longitudinal sides of the bare cell101, and the first and second side walls575and585are positioned at the narrow sides of the bare cell101. However, the case504may be formed as an integrated body, or may be configured such that the coupling regions C are disposed adjacent to the longitudinal sides of the bare cell101, such that the first and second side walls575and585are disposed adjacent to the longitudinal sides of the bare cell101.

Although not depicted in the drawings, the first and second side walls575and585of the case504, may include coupling parts to interlock the first and second side walls575and585, as described with regard to the cases500and502.

The clips540may be any device which is positioned at the coupling region C and attaches the first case body570to the second case body580, such that a molding material (such as resin or hot melt), which is introduced into the case504during the molding, does not leak out. The clips540may also be used with the cases500and502. Additional clips540may also be used, such that clips540are disposed on both ends of the coupling region C. When described as clips, it is understood that any pressing mechanism can be used combine the sides575,585in addition to or instead of the clips540.

Therefore, according to aspects of the present invention, the various side walls of the cases include coupling parts, or include tabs, to couple together the various first and second case bodies, so that the molding material, such as, the resin or the hot melt, which is introduced into the case during the molding, is prevented from leaking through the side walls of the cases.