Abstract:
A rechargeable battery includes an electrode assembly; a can housing the electrode assembly and having an open end, a bottom surface substantially opposite to the open end, a first planar surface and a second planar surface, wherein the first planar surface and the second planar surface each have a first fracture portion that facilitates buckling of the can under compression, wherein a first axis is defined extending from the bottom surface to the open end, and wherein the first fracture portion extends along a second axis in a direction substantially perpendicular to the first axis; and a cap plate sealing the open end of the can.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of U.S. Provisional Application No. 61/330,841 filed in the U.S. Patent and Trademark Office on May 3, 2010, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the present invention relates to a rechargeable battery. 
     2. Description of the Related Art 
     Unlike a primary battery, a rechargeable battery (i.e., a secondary battery) can be repeatedly recharged and discharged. Typical rechargeable batteries include a nickel-hydrogen battery, a lithium battery, a lithium ion battery, and the like. Rechargeable batteries may be manufactured in the form of a pack, and are commonly employed for mobile electronic devices such as cellular phones, notebook computers, and camcorders. 
     A rechargeable battery typically includes a jelly roll type of electrode assembly formed by winding a positive electrode and a negative electrode with a separator located therebetween in a stacked manner, a can accommodating the electrode assembly and electrolyte therein, and a cap assembly hermetically sealing an upper opening of the can. 
     The can is often made of aluminum or an aluminum alloy, and has a cylindrical or angular shape. When pressure acts in the direction perpendicular to a vertical direction of the angular can, that is, when a longitudinal compression occurs, a lower bottom face of the can be folded to be pushed inward to damage the electrode assembly, short circuiting the positive electrode and negative electrode. Then, the rechargeable battery may combust or explode. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     Embodiments of the present invention have been made in an effort to provide a rechargeable battery that is stable even under longitudinal compression. Embodiments of the present invention have also been made in an effort to provide a rechargeable battery capable of preventing significant damage to an electrode assembly due to longitudinal compression of the battery, thus preventing or reducing the likelihood of combustion or explosion. 
     An exemplary embodiment of the present invention provides a rechargeable battery including an electrode assembly; a can housing the electrode assembly and having an open end, a bottom surface substantially opposite to the open end, a first planar surface and a second planar surface, wherein the first planar surface and the second planar surface each have a first fracture portion that facilitates buckling of the can under compression, wherein a first axis is defined extending from the bottom surface to the open end, and wherein the first fracture portion extends along a second axis in a direction substantially perpendicular to the first axis; and a cap plate sealing the open end of the can. 
     In one embodiment, the first fracture portion is a groove. Further, the first fracture portion may be proximate to the open end of the can and/or proximate to and spaced from the bottom surface of the can. Additionally, the first fracture portion on the first planar surface may substantially correspond to the first fracture portion on the second planar surface. 
     In one embodiment, a second fracture portion is on the first planar surface and on the second planar surface and a first fold portion on the first planar surface. The first fold portion may be spaced from at least one of the first fracture portion and the second fracture portion or may contact both fracture portions. 
     According to an exemplary embodiment of the present invention, because the fracture portions are provided on the front and rear faces in the vicinity of the bottom face of the can, when the can is compressed to be deformed due to a longitudinal compression, the fracture portion is buckled or fractured to make the bottom face of the can fold toward an outer side of the can, thereby preventing damage to the electrode assembly by the deformed bottom face. Therefore, the positive electrode and the negative electrode can be prevented from being short-circuited, and combustion or explosion of the rechargeable battery can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a rechargeable battery according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view taken along line II-II in a state in which the rechargeable battery of  FIG. 1  is assembled. 
         FIG. 3  is a cross-sectional view taken along line III-III in the state in which the rechargeable battery of  FIG. 1  is assembled. 
         FIG. 4(   a ) is a front view of the rechargeable battery of  FIG. 2 , and  FIG. 4(   b ) is a rear view of the rechargeable battery of  FIG. 2 . 
         FIG. 5  is a perspective view showing test results of a longitudinal compression of the rechargeable battery of  FIG. 4 . 
         FIG. 6  is a cross-sectional perspective view taken along ling VI-VI in  FIG. 5 ; 
         FIG. 7  is a cross-sectional view taken along line VII-VII in  FIG. 5 ; 
         FIG. 8(   a ) is a front view of a rechargeable battery according to a second exemplary embodiment of the present invention, and  FIG. 8(   b ) is a rear view of the rechargeable battery according to the second exemplary embodiment of the present invention. 
         FIG. 9  is a perspective view showing test results of a longitudinal compression of the rechargeable battery of  FIG. 8 . 
         FIG. 10  is a cross-sectional perspective view taken along line X-X in  FIG. 9 . 
         FIG. 11  is a cross-sectional perspective view taken along line XI-XI in  FIG. 9 . 
         FIG. 12(   a ) is a front view of a rechargeable battery according to a third exemplary embodiment of the present invention, and  FIG. 12(   b ) is a rear view of the rechargeable battery according to the third exemplary embodiment of the present invention. 
         FIG. 13(   a ) is a front view of a rechargeable battery according to a fourth exemplary embodiment of the present invention, and  FIG. 13(   b ) is a rear view of the rechargeable battery according to the fourth exemplary embodiment of the present invention. 
         FIG. 14(   a ) is a front view of a rechargeable battery according to a fifth exemplary embodiment of the present invention, and  FIG. 14(   b ) is a rear view of the rechargeable battery according to the fifth exemplary embodiment of the present invention. 
         FIG. 15(   a ) is a front view of a rechargeable battery according to a sixth exemplary embodiment of the present invention, and  FIG. 15(   b ) is a rear view of the rechargeable battery according to the sixth exemplary embodiment of the present invention. 
         FIG. 16(   a ) is a front view of a rechargeable battery according to a seventh exemplary embodiment of the present invention, and  FIG. 16(   b ) is a rear view of the rechargeable battery according to the seventh exemplary embodiment of the present invention. 
         FIG. 17(   a ) is a front view of a rechargeable battery according to an eighth exemplary embodiment of the present invention, and  FIG. 17(   b ) is a rear view of the rechargeable battery according to the eighth exemplary embodiment of the present invention. 
         FIG. 18(   a ) is a front view of a rechargeable battery according to a ninth exemplary embodiment of the present invention, and  FIG. 18(   b ) is a rear view of the rechargeable battery according to the ninth exemplary embodiment of the present invention. 
         FIG. 19(   a ) is a front view of a rechargeable battery according to a tenth exemplary embodiment of the present invention, and  FIG. 19(   b ) is a rear view of the rechargeable battery according to the tenth exemplary embodiment of the present invention. 
         FIG. 20(   a ) is a front view of a rechargeable battery according to an eleventh exemplary embodiment of the present invention, and  FIG. 20(   b ) is a rear view of the rechargeable battery according to the eleventh exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
       FIG. 1  is an exploded perspective view of a rechargeable battery according to a first exemplary embodiment of the present invention, and  FIG. 2  is a cross-sectional view taken along line II-II in a state in which the rechargeable battery of  FIG. 1  is assembled. With reference to  FIGS. 1 and 2 , a rechargeable battery  100  according to the first exemplary embodiment of the present invention includes an electrode assembly  10 , a can  20  accommodating the electrode assembly  10  along with an electrolyte therein, and a cap assembly  30  hermetically sealing an opening formed at an upper end of the can  20 . 
     The electrode assembly  10  is formed by spiral-winding a positive electrode  4  and a negative electrode  6  with a separator  2  located therebetween in the form of a jelly roll. The electrode assembly  10  has a shape generally corresponding to an internal space of the angular can  20  so as to fit into the interior of the can  20 . 
     The can  20  receives the electrode assembly  10  through the opening formed at one side thereof, and is formed as a conductor to be able to serve as an electrode terminal. For example, the can  20  is made of aluminum or an aluminum alloy, and is electrically connected with the positive electrode  4  of the electrode assembly  10  to act as a positive terminal. In this case, an electrode terminal  31  provided to the cap assembly  30  is electrically connected with the negative electrode  6  of the electrode assembly to act as a negative terminal. Conversely, the can  20  may serve as a negative terminal, and the electrode terminal  31  may act as a positive terminal. 
     The cap assembly  30  includes a cap plate  32  fixed to the opening of the can  20 , the electrode terminal  31  inserted into a terminal hole  32   a  of the cap plate  32  with an insulating gasket  33  located therebetween, a terminal plate  34  electrically connected with a lower end of the electrode terminal  31 , an insulating plate  36  positioned between the cap plate  32  and the terminal plate  34 , and an insulating case  37  insulating the electrode assembly  10  and the cap assembly  30 . The insulating gasket  33  electrically insulates the electrode terminal  31  and the cap plate  32 , and the insulating plate  36  electrically insulates the terminal plate  34  and the cap plate  32 . 
     A positive lead  11  fixed to the positive electrode  4  of the electrode assembly  10  is welded to an inner surface of the cap plate  32  to transfer current of the positive electrode  4  to the cap plate  32  and the can  20 . That is, the can  20  acts as a positive terminal. Also, a negative lead  12  fixed to the negative electrode  6  of the electrode assembly  10  is welded to a lower surface of the terminal plate  34  to transfer current of the negative electrode  6  to the terminal plate  34  and the electrode terminal  31 . That is, the electrode terminal  31  acts as a negative terminal. 
       FIG. 3  is a cross-sectional view taken along line III-III in the state in which the rechargeable battery of  FIG. 1  is assembled,  FIG. 4(   a ) is a front view of the rechargeable battery of  FIG. 2 , and  FIG. 4(   b ) is a rear view of the rechargeable battery of  FIG. 2 . With reference to  FIGS. 3 ,  4 ( a ), and  4 ( b ), the can  20  has an angular shape and includes the opening, a first face (referred to as a “front face” or a “first planar surface” hereinafter)  21 , a second face (referred to as a “rear face” or a “second planar surface” hereinafter)  22 , and a third face (referred to as a “bottom face” or “bottom surface” hereinafter)  23  to form an accommodating space of the electrode assembly  10 . In the first exemplary embodiment, the angular can  20  is configured to have sufficient stability to minimize damage the electrode assembly  10  under longitudinal compression. 
     In one embodiment, the front face  21  and the rear face  22  of the can  20  include at least first fracture portions  51  and  61  in the vicinity of or proximate to the bottom face  23 . The first fracture portions  51  and  61  are exemplarily formed as grooves or notches on the front face  21  and the rear face  22  at corresponding positions and spaced from the bottom face  23  to facilitate buckling or fracturing of the front face  21  and the rear face  22  under compression. 
     The first fracture portions  51  and  61  may be formed on the front face  21  and the rear face  22  and have lengths L 51  and L 61 , respectively, which may be equal to or less than widths W 21  and W 22  of the front face  21  and the rear face  22  along the widthwise direction. For example, in order for the first fracture portions  51  and  61  to effectively induce the front face  21  and the rear face  22  to be fractured, the lengths L 51  and L 61  of the first fracture portions  51  and  61  may be about 80 percent or greater of the widths W 21  and W 22 . The first fracture portions  51  and  61  are formed to be substantially symmetrical on the front face  21  and the rear face  22  to thus induce a generally symmetrical deformation of the can  20  in the occurrence of a threshold longitudinal compression. 
     The can  20  includes the first fracture portions  51  and  61  in the vicinity of the bottom face  23  to correspond to deformation caused by a longitudinal compression. Further, the can  20  may include second fracture portions  52  and  62  in the vicinity of the cap plate  32  to more effectively cope with a deformation caused by a longitudinal compression. 
     In one embodiment, the front face  21  and the rear face  22  of the can  20  further include the second fracture portions  52  and  62  in the vicinity of the cap plate  32 . The second fracture portions  52  and  62  may be exemplarily formed as grooves or notches on the front face  21  and the rear face  22  at corresponding positions spaced from the cap plate  32  to facilitate fracturing of the front face  21  and the rear face  22 . 
     The second fracture portions  52  and  62  are formed on the front face  21  and the rear face  22  and may have lengths L 52  and L 62 , respectively, which may be equal to or less than the widths W 21  and W 22  of the front face  21  and the rear face  22  along the widthwise direction. For example, in order for the second fracture portions  52  and  62  to effectively induce the front face  21  and the rear face  22  to buckle or fracture, the lengths L 52  and L 62  of the second fracture portions  52  and  62  may be about 80 percent or greater of the widths W 21  and W 22 . Also, the second fracture portions  52  and  62  are formed to be substantially symmetrical on the front face  21  and the rear face  22  to thus induce a generally symmetrical deformation of the can  20  under longitudinal compression. 
     In addition, the pair of first fracture portions  51  and  61  in the vicinity of the bottom face  23  and the pair of second fracture portions  52  and  62  in the vicinity of the cap plate  32  are formed to be substantially symmetrical on both sides of the can  20  in a vertical lengthwise direction parallel to length (L) to induce a generally symmetrical deformation under longitudinal compression. 
     With reference to  FIG. 3 , the first fracture portions  51  and  61  and the second fracture portions  52  and  62  may have a notch width (W) of between about 0.1 mm to about 0.5 mm, and a thickness (T) of the case at the notch may be between about 0.1 mm to about 0.15 mm. There may be a difference in the material of the can  20 , but when the can  20  is made of an aluminum alloy, if the notch width (W) is less than 0.1 mm, a fracture inducement effect may be too weak, and if the notch width (W) is larger than 0.5 mm, the durability of the can  20  could be impaired. If the thickness (T) of the can  20  at the notch is less than 0.1 mm, the durability of the can  20  could be impaired, while if it exceeds 0.15 mm, the fracture inducement effect could be too weak. Thus, in order to facilitate the fracture inducement without degrading the durability of the can  20 , the can  20  may be formed such that the notch width (W) is maximized while the thickness (T) of the remaining portion is minimized based on the material of the can  20  and the usage environment of the rechargeable battery  100 . 
     The first fracture portions  51  and  61  are formed to be spaced from the bottom face  23  such that they are positioned within about 10 percent of the vertical length (L) of the can  20 , so that when the first fracture portions  51  and  61  buckle or fracture, the bottom face  23  can buckle or fracture without being interfered with by the electrode assembly  10 , thus effectively preventing the bottom face  23  from being pushed toward the electrode assembly  10 . The second fracture portions  52  and  62  are formed to be spaced from the cap plate  32  such that they are positioned within about 25% of the vertical length (L) of the can  20 , so that when the second fracture portions  52  and  62  fracture, the cap plate  32  can be buckled or fractured without being interfered with by the electrode assembly  10 , thus effectively preventing the cap plate  32  from being pushed toward the electrode assembly  10 . 
       FIG. 5  is a perspective view showing test results of a longitudinal compression of the rechargeable battery of  FIG. 4 ,  FIG. 6  is a cross-sectional perspective view taken along line VI-VI in  FIG. 5 , and  FIG. 7  is a cross-sectional view taken along line VII-VII in  FIG. 5 . With reference to  FIGS. 5 to 7 , when the can  20  is compressed and deformed due to a longitudinal compression of the rechargeable battery  100 , the first fracture portions  51  and  61  are fractured by the lengths L 51  and L 61  near the bottom face  23 , allowing the bottom face to be folded from the exterior of the can  20 . Accordingly, the bottom face  23  can be deformed without being forced into the electrode assembly  10  or damaging the electrode assembly  10 . That is, the positive electrode  4  and the negative electrode  6  may not be short-circuited despite deformation of the bottom face  23 . 
     Also, when the can  20  is compressed and deformed due to a longitudinal compression of the rechargeable battery  100 , the second fracture portions  52  and  62  are fractured by the lengths L 52  and L 62  near the cap plate  32 , allowing cap plate  32  to be folded from the exterior of the can  20 . Accordingly, only the cap plate  32  is deformed without being brought into contact with the electrode assembly  10  or damaging the electrode assembly  10 . That is, a short circuit of the positive electrode  4  and the negative electrode  6  can be avoided despite deformation of cap plate  32 . 
     The bottom face  23  is deformed in a state of being tightly attached to the electrode assembly  10 , while the cap plate  32  is deformed in a state of being spaced from the electrode assembly  120  with the insulating case  37  located therebetween. When the rechargeable battery  100  is deformed by a longitudinal compression, the cap assembly  30  is less likely to damage the electrode assembly  10  than the bottom face  23 . Thus, the front face  21  and the rear face  22  may include one of the first fracture portions  51  and  61  and the second fracture portions  52  and  62 , or in the first exemplary embodiment, the front face  21  and the rear face  22  may include both the first fracture portions  51  and  61  and the second fracture portions  52  and  62 . In this case, the presence of the first fracture portions  51  and  61  and the second fracture portions can prevent significant damage to the electrode assembly  10  at the portions in the vicinity of the bottom face  23  and the cap plate  32  and also prevent or reduce the likelihood of a short-circuit of the positive electrode  4  and the negative electrode  6 . 
     Various other exemplary embodiments of the present invention will now be described by comparing them with the first exemplary embodiment and foregoing exemplary embodiments of the present invention. 
       FIG. 8(   a ) is a front view of a rechargeable battery according to a second exemplary embodiment of the present invention, and  FIG. 8(   b ) is a rear view of the rechargeable battery according to the second exemplary embodiment of the present invention. Referring to the first exemplary embodiment of the present invention, the first fracture portions  51  and  61  and the second fracture portions  52  and  62  of the rechargeable battery  100  according to the first exemplary embodiment of the present invention have substantially the same structure. In comparison, with reference to  FIG. 8 , in the rechargeable battery  200  according to the second exemplary embodiment of the present invention, first fracture portions  251  and  61  have different structures, second fracture portions  252  and  62  have different structures, and a fold portion  271  is formed on the front face  21 . 
     For example, the first and second fracture portions  251  and  252  on the front face  21  are formed to have substantially the same structure, and the first and second fracture portions  61  and  62  on the rear face  22  are formed to have substantially the same structure. The first fracture portions  251  and  61  are formed to be different in the vicinity of the bottom face  23 , and the second fracture portions  252  and  62  are formed to be different in the vicinity of the cap plate  32 . The pairs of first fracture portions  251  and  61  and second fracture portions  252  and  62  are generally symmetrical. 
     The first and second fracture portions  61  and  62  on the rear face  22  have the substantially the same shape and substantially the same fracture performance as those in the first exemplary embodiment of the present invention. The first and second fracture portions  251  and  252  on the front face  21  are formed at the central portion of the front face  21  in a widthwise direction, and lengths L 251  and L 252  of the first and second fracture portions  251  and  252  are shorter than the widths W 21  of the front face  21 . For example, the lengths L 251  and L 252  of the first and second fracture portions  251  and  252  on the front face  21  are about 30% of the size of the width W 21  of the front face  21  or greater to minimize buckling or fracturing in the vicinity of the bottom face  23  and the cap plate  32 . 
     The fold portion  271  is formed as a notch extending in a vertical lengthwise direction of the can  20  between the first and second fracture portions  251  and  252 . The length L 271  of the fold portion  271  is longer than the lengths L 251  and L 252  of the first and second fracture portions  251  and  252  on the front face  21 . When the first and second fracture portions  251  and  252  minimize fracturing, the fold portion  271  induces the front face  21  to be folded under longitudinal compression to accelerate fracturing of the first and second fracture portions  61  and  62  on the rear face  22 . That is, the presence of the fold portion  271  supplements lower fracturing performance of the first and second fracture portions  251  and  252  that are shorter on the front face  21  through folding of the front face  21  and accelerating fracturing of the rear face  22 . 
     The length L 271  of the fold portion  271  may be about 80% or greater of the distance (C) between the first and second fracture portions  251  and  252  of the front face  21 . Also, the length L 271  may be equal to the distance (C). If the length L 271  of the fold portion  271  is less than 80 percent of the distance (C) between the first and second fracture portions  251  and  252 , a folding inducement performance of the front face  21  under longitudinal compression could deteriorate and fracturing of the first and second fracture portions  61  and  62  of the rear face  22  may be hampered. 
       FIG. 9  is a perspective view showing test results of a longitudinal compression of the rechargeable battery of  FIG. 8 ,  FIG. 10  is a cross-sectional perspective view taken along line X-X in  FIG. 9 , and  FIG. 11  is a cross-sectional perspective view taken along line XI-XI in  FIG. 9 . With reference to  FIGS. 8 to 11 , when the can  20  is compressed to be deformed by a longitudinal compression of the rechargeable battery  200 , the first and second fracture portions  61  and  62  on the rear face  22  are fractured by the lengths L 61  and L 62  in the vicinity of the bottom face  23  and the cap plate  32 , allowing the bottom face  23  and the cap plate  32  to be folded outside the can  20 . 
     Simultaneously, the first and second fracture portions  251  and  252  are fractured by the lengths L 251  and L 252  in the vicinity of the bottom face  23  and the cap plate  32 . Also, because the front face  21  is fractured to be shorter than the rear face  22 , it is folded along the fold portion  271  inwardly with respect to the rear face  22  (see  FIGS. 9 and 11 ). 
     In the rechargeable battery  200  according to the second exemplary embodiment of the present invention, the can  20  is deformed in contact with the electrode assembly  10  at the inner side of the can  20 . Because the fold portion  271  formed on the front face  21  of the can  20  accelerates fracturing of the first and second fracture portions  61  and  62  of the rear face  22 , a dispersion influence of the notch processing at the first fracture portions  251  and  61  and the second fracture portions  252  and  62  can be reduced. Thus, because only the bottom face  23  and the cap plate  32  are deformed, they are not brought into contact with the electrode assembly  10  nor do they damage the electrode assembly  10 . That is, the positive electrode  4  and the negative electrode  6  are not short-circuited by the deformed bottom face  23  and the cap plate  32 . 
       FIG. 12(   a ) is a front view of a rechargeable battery according to a third exemplary embodiment of the present invention, and  FIG. 12(   b ) is a rear view of the rechargeable battery according to the third exemplary embodiment of the present invention. Referring to the rechargeable battery  200  according to the second exemplary embodiment, the fold portion  271  is formed as a single line, but a fold portion  371  of a rechargeable battery  300  according to the third exemplary embodiment of the present invention is formed as two lines. Like the rechargeable battery  200  according to the second exemplary embodiment of the present invention, the rechargeable battery  300  according to the third exemplary embodiment of the present invention includes the first and second fracture portions  251  and  252  formed on the front face  21  and the first and second fracture portions  61  and  62  formed on the rear face  22 . 
     In the rechargeable battery  300  according to the third exemplary embodiment of the present invention, the two-line fold portions  371  are formed to have a substantially symmetrical structure based on a central line extending in a lengthwise direction at the center of the width W 21  on the front face  21 . The two-line fold portions  371  are formed in the lengthwise direction of the can  20  between the first and second fracture portions  251  and  252  on the front face  21  to induce two areas or at least one area of the front face  21  to be folded under longitudinal compression, further accelerating fracturing of the first and second fracture portions  61  and  62  on the rear face  22 . In this case, a space C 371  between the fold portions  371  is between about 5 mm and 8 mm. If the space C 371  is less than 5 mm, at least one of the two lines is less likely to be folded, and if the space C 371  exceeds 8 mm, the front face  21  could be folded asymmetrically or it may be too difficult for the front face  21  to be folded. 
       FIG. 13(   a ) is a front view of a rechargeable battery according to a fourth exemplary embodiment of the present invention, and  FIG. 13(   b ) is a rear view of the rechargeable battery according to the fourth exemplary embodiment of the present invention. Referring to the rechargeable battery  300  according to the third exemplary embodiment of the present invention, the fold portions  371  are formed to be spaced from the first and second fracture portions  251  and  252  of the front face  21 . That is, the length L 371  of the fold portions  371  is shorter than the distance (C) between the first and second fracture portions  251  and  252 . In comparison, in a rechargeable battery  400  according to the fourth exemplary embodiment of the present invention, fold portions  471  are connected with the first and second fracture portions  251  and  252  on the front face  21 . That is, a length L 471  of the fold portions  471  is substantially equal to the distance (C) between the first and second fracture portions  251  and  252 . In the fourth exemplary embodiment of the present invention, the length L 471  of the fold portions  471  is longer than the length L 371  of the fold portions  371  in the third exemplary embodiment of the present invention, so folding of the front face  21  can be more effectively induced. That is, in the fourth exemplary embodiment of the present invention, the fold portions  471  may cause or induce the front face  21  from the vicinity of the bottom face  23  to the vicinity of the cap plate  32  to be folded. 
       FIG. 14(   a ) is a front view of a rechargeable battery according to a fifth exemplary embodiment of the present invention, and  FIG. 14(   b ) is a rear view of the rechargeable battery according to the fifth exemplary embodiment of the present invention. With reference to  FIG. 14 , a rechargeable battery  500  according to the fifth exemplary embodiment of the present invention additionally includes first and second fold portions  571  and  572  in the rechargeable battery  100  according to the first exemplary embodiment of the present invention. 
     The first fold portion  571  is formed as a groove or notch extending in the vertical lengthwise direction of the can  20  between the first and second fracture portions  51  and  52  at the center of the width W 21  on the front face  21 . The first fold portion  571  is connected with the first and second fracture portions  51  and  52  of the front face  21 . That is, the length L 571  of the first fold portion  571  is substantially equal to the distance (C) between the first and second fracture portions  51  and  52 . 
     The second fold portion  572  is formed as a notch extending in the vertical lengthwise direction of the can  20  between the first and second fracture portions  61  and  62  at the center of the width W 22  on the rear face  22 . The second fold portion  572  is connected to the first and second fracture portions  61  and  62  of the rear face  22 . That is, the length L 572  of the second fold portion  572  is equal to the distance (C) between the first and second fracture portions  61  and  62 . 
     Under longitudinal compression, the first fold portion  571  induces the front face  21  to be folded from the vicinity of the bottom face  23  to the vicinity of the cap plate  32  to accelerate fracturing of the first and second fracture portions  61  and  62  on the rear face  22 . Additionally, under longitudinal compression, the second fold portion  572  induces the rear face  22  to be folded from the vicinity of the bottom face  23  to the vicinity of the cap plate  32  to accelerate fracturing of the first and second fracture portions  51  and  52  on the front face  21 . That is, when the rechargeable battery  500  undergoes longitudinal compression according to the fifth exemplary embodiment of the present invention, the front face  21  or the rear face  22  may be folded to be turned toward an inner side or an outer side. 
       FIG. 15(   a ) is a front view of a rechargeable battery according to a sixth exemplary embodiment of the present invention, and  FIG. 15(   b ) is a rear view of the rechargeable battery according to the sixth exemplary embodiment of the present invention. Referring to the rechargeable battery  500  according to the fifth exemplary embodiment of the present invention, the first and second fold portions  571  and  572  connect the first and second fracture portions  51  and  52  of the front face and the first and second fracture portions  61  and  62  of the rear face  22 . In comparison, in a rechargeable battery  600  according to the sixth exemplary embodiment of the present invention, first and second fold portions  671  and  672  are spaced from the first and second fracture portions  51  and  52  of the front face  21  and spaced from the first and second fracture portions  61  and  62  of the rear face  22 . 
     With reference to  FIG. 15 , in the rechargeable battery  600  according to the sixth exemplary embodiment of the present invention, a length L 671  of the first fold portion  671  is shorter than the distance (C) between the first and second fracture portions  51  and  52 , and a length L 672  of the second fold portion  672  is shorter than the distance (C) between the first and second fracture portions  61  and  62 . 
     In the occurrence of a longitudinal compression, the first fold portion  671  induces the front face  21  to be folded to accelerate fracturing of the first and second fracture portions  61  and  62  on the rear face  22 , and the second fold portion  672  induces the rear face  22  to be folded to accelerate fracturing of the first and second fracture portions  51  and  52  on the front face  21 . That is, when a longitudinal compression occurs to the rechargeable battery  600  according to the sixth exemplary embodiment of the present invention, the front face  21  or the rear face  22  may be folded to be turned towards an inner side or an outer side. 
       FIG. 16(   a ) is a front view of a rechargeable battery according to a seventh exemplary embodiment of the present invention, and  FIG. 16(   b ) is a rear view of the rechargeable battery according to the seventh exemplary embodiment of the present invention. Referring to the rechargeable battery  200  according to the second exemplary embodiment of the present invention, the fold portion  271  is spaced from the first and second fracture portions  251  and  252  on the front face  21 . In comparison, in a rechargeable battery  700  according to the seventh exemplary embodiment of the present invention, a fold portion  771  is connected to the first and second fracture portions  251  and  252  on the front face  21 . 
     With reference to  FIG. 16 , in the rechargeable battery  700  according to the seventh exemplary embodiment of the present invention, the fold portion  771  has a length L 771  which is substantially equal to the distance (C) between the first and second fracture portions  251  and  252 , to thus effectively cause the front face  21  to be folded, compared with the second exemplary embodiment of the present invention. That is, according to the seventh exemplary embodiment of the present invention, the fold portion  771  induces the front face  21  to be folded from the vicinity of the bottom face  23  to the vicinity of the cap plate  32 . 
       FIG. 17(   a ) is a front view of a rechargeable battery according to an eighth exemplary embodiment of the present invention, and  FIG. 17(   b ) is a rear view of the rechargeable battery according to the eighth exemplary embodiment of the present invention. Referring to the rechargeable battery  200  according to the second exemplary embodiment of the present invention, the fold portion  271  is spaced from the first and second fracture portions  251  and  252  on the front face  21 . In comparison, in a rechargeable battery  800  according to the eighth exemplary embodiment of the present invention, a fold portion  871  is spaced from the first fracture portion  251  on the front face  21  and connected to the second fracture portion  252  on the front face  21 . 
     With reference to  FIG. 17 , in the rechargeable battery  800  according to the eighth exemplary embodiment of the present invention, the fold portion  971 , having a length L 871  shorter than the distance (C) between the first and second fracture portions  251  and  252 , induces the front face  21  to be folded. In the eighth exemplary embodiment of the present invention, because the fold portion  871  induces the front face  21  to be folded up to the vicinity of the cap plate  32 , more of the front face  21  can be folded in the vicinity of the cap plate  32  than in the vicinity of the bottom face  23 . 
       FIG. 18(   a ) is a front view of a rechargeable battery according to a ninth exemplary embodiment of the present invention, and  FIG. 18(   b ) is a rear view of the rechargeable battery according to the ninth exemplary embodiment of the present invention. Referring to the rechargeable battery  200  according to the second exemplary embodiment of the present invention, the fold portion  271  is spaced from the first and second fracture portions  251  and  252  on the front face  21 . In comparison, in a rechargeable battery  900  according to the ninth exemplary embodiment of the present invention, a fold portion  971  is spaced from the second fracture portion  252  on the front face  21  and connected with the first fracture portion  251  on the front face  21 . 
     With reference to  FIG. 18 , in the rechargeable battery  900  according to the ninth exemplary embodiment of the present invention, the fold portion  971 , having a length L 971  shorter than the distance (C) between the first and second fracture portions  251  and  252 , induces the front face  21  to be folded. In the ninth exemplary embodiment of the present invention, because the fold portion  971  induces the front face  21  to be folded up to the vicinity of the bottom face  23 , more of the front face  21  can be folded in the vicinity of the bottom face  23  than in the vicinity of the cap plate  32 . 
       FIG. 19(   a ) is a front view of a rechargeable battery according to a tenth exemplary embodiment of the present invention, and  FIG. 19(   b ) is a rear view of the rechargeable battery according to the tenth exemplary embodiment of the present invention. Referring to the rechargeable battery  300  according to the third exemplary embodiment of the present invention, the fold portions  371  formed as two lines are spaced from the first and second fracture portions  251  and  252  on the front face  21 . In comparison, in a rechargeable battery  1000  according to the tenth exemplary embodiment of the present invention, fold portions  1071  formed as two lines are spaced from the first fracture portion  251  on the front face  21  and connected with the second fracture portion  252  on the front face  21 . 
     With reference to  FIG. 19 , in the rechargeable battery  1000  according to the tenth exemplary embodiment of the present invention, the fold portions  1071 , having a length L 1071  shorter than the distance (C) between the first and second fracture portions  251  and  252 , induce the front face  21  to be folded. In the tenth exemplary embodiment of the present invention, because the fold portions  1071  induce the front face  21  to be folded up to the vicinity of the cap plate  32 , more of the front face  21  can be folded in the vicinity of the cap plate  32  than in the vicinity of the bottom face  23 . 
       FIG. 20(   a ) is a front view of a rechargeable battery according to an eleventh exemplary embodiment of the present invention, and  FIG. 20(   b ) is a rear view of the rechargeable battery according to the eleventh exemplary embodiment of the present invention. Referring to the rechargeable battery  300  according to the third exemplary embodiment of the present invention, the fold portions  371  formed as two lines are spaced from the first and second fracture portions  251  and  252  on the front face  21 . In comparison, in a rechargeable battery  1100  according to the eleventh exemplary embodiment of the present invention, fold portions  1171  formed as two lines are connected to the first fracture portion  251  on the front face  21  and spaced from the second fracture portion  252  on the front face  21 . 
     With reference to  FIG. 20 , in the rechargeable battery  1100  according to the eleventh exemplary embodiment of the present invention, the fold portions  1171 , having a length L 1171  shorter than the distance (C) between the first and second fracture portions  251  and  252 , induce the front face  21  to be folded. In the eleventh exemplary embodiment of the present invention, because the fold portions  1171  induce the front face  21  to be folded up to the vicinity of the bottom face  23 , more of the front face  21  can be folded in the vicinity of the bottom face  23  than in the vicinity of the cap plate  32 . 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     
       
         
               
             
               
             
               
               
             
               
             
               
               
             
               
             
               
               
             
           
               
                   
               
               
                 Description of Symbols 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100: rechargeable 
               
               
                 battery 
               
             
          
           
               
                 2: separator 
                 4: positive electrode 
               
               
                 6: negative electrode 
                 10: electrode assembly 
               
               
                 20: can 
                 21: first face (front face) 
               
               
                 22: second face (rear face) 
                 23: third face (bottom face) 
               
               
                 30: cap assembly 
                 31: electrode terminal 
               
               
                 32: cap plate 
                 33: Insulating gasket 
               
               
                 32a: terminal hole 
                 34: terminal plate 
               
               
                 36: insulating plate 
                 37: insulating case 
               
             
          
           
               
                 51, 61, 251: first fracture portion 
               
               
                 52, 62, 252: second fracture portion 
               
               
                 271, 371, 471, 771, 871, 971, 1071, 1171: fold portion 
               
             
          
           
               
                 571, 671: first fold portion 
                 572, 672: second fold portion 
               
               
                 C: distance 
                 L: vertical length 
               
             
          
           
               
                 L51, L61, L251, L252, L271, L371, L471, L571, L572, L671, L672, 
               
               
                 L771, L871, L971, L1071, L1171: length 
               
               
                 T: thickness of remaining portion 
               
             
          
           
               
                 W: notch width 
                 W21, W22: width