Abstract:
A rechargeable battery is disclosed. The rechargeable battery comprises: a central electrode portion comprising a positive electrode, a negative electrode and a separator; a first electrode portion extending from a first end of the central electrode portion; a second electrode portion extending from a second end of the central electrode portion opposite the first end; a central case enclosing the central electrode portion; a first electrode case enclosing the first electrode portion, wherein the first electrode case is coupled to the central case such that an overlapping part of the first electrode case encloses a part of the central electrode portion at the first end, and the central case encloses the overlapping part of the first electrode case; and a second electrode case enclosing the second electrode portion, wherein the second electrode case is coupled to the central case such that an overlapping part of the second electrode case encloses a part of the central electrode portion at the second end, and the central case encloses the overlapping part of the second electrode case.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application No. 61/251,243, filed on Oct. 13, 2009, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a rechargeable battery. More particularly, the present disclosure relates to a structure of a case that houses an electrode group. 
     2. Description of the Related Technology 
     A rechargeable battery typically includes an electrode group that includes an positive electrode, a separator, and a negative electrode, a case that houses the electrode group, and an electrode terminal that is connected to the electrode group and that is drawn out to the outside of the case. The case can be formed with a laminate sheet in which a metal layer and a resin layer are bonded, and a rechargeable battery having the case is referred to as a pouch type battery. 
     A common pouch type battery is typically formed by fixing a positive electrode terminal and a negative electrode terminal by welding to a positive electrode uncoated portion and a negative electrode uncoated portion, respectively, of the electrode group, housing the entire electrode group, a part of the positive electrode terminal and the negative electrode terminal in the internal space of the case with an electrolyte solution. The battery is then typically sealed by bonding edges of the upper case and the lower case by thermal bonding. 
     However, in the above-described structure, a welding portion of the electrode group and the electrode terminal, a sealing portion of the upper case and the lower case, and a drawn-out portion of the electrode terminal are sequentially positioned at the outside of the electrode group. Therefore, because a portion that does not contribute to an actual battery reaction in the entire rechargeable battery occupies a large area, the entire volume is expanded. Thus, it is disadvantageous to form the rechargeable battery to have high capacity and a compact size. 
     Moreover, when thermal bonding the upper case and the lower case, the upper case is sealed to the lower case by deep drawing the upper case. In this case, because the edge of the upper case becomes weak by the deep drawing, the case can be easily damaged by an external impact, and thus reliability of the rechargeable battery is deteriorated. 
     The above is only provided to enhance 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 provide for a rechargeable battery having the advantages of high capacity and a compact size by reducing the area of a portion that does not contribute to battery reactions outside the electrode group. 
     An embodiment of the present invention provides a rechargeable battery comprising: a central electrode portion comprising a positive electrode, a negative electrode and a separator; a first electrode portion extending from a first end of the central electrode portion; a second electrode portion extending from a second end of the central electrode portion opposite the first end; a central case enclosing the central electrode portion; a first electrode case enclosing the first electrode portion, wherein the first electrode case is coupled to the central case such that an overlapping part of the first electrode case encloses a part of the central electrode portion at the first end, and the central case encloses the overlapping part of the first electrode case; and a second electrode case enclosing the second electrode portion, wherein the second electrode case is coupled to the central case such that an overlapping part of the second electrode case encloses a part of the central electrode portion at the second end, and the central case encloses the overlapping part of the second electrode case. 
     According to another embodiment, a rechargeable battery comprises: a central electrode portion comprising a positive electrode, a negative electrode and a separator; a first electrode portion extending from a first end of the central portion; a second electrode portion extending from a second end of the central portion opposite the first end; a central case enclosing the central electrode portion; a first electrode case enclosing the first electrode portion; and a second electrode case enclosing the second electrode portion; wherein at least one of the first or second electrode cases is bent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rechargeable battery according to one embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of the rechargeable battery shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the rechargeable battery of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a rechargeable battery according to another embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of a rechargeable battery according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described more fully hereinafter with reference to the accompanying drawings. 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. 
       FIG. 1  is a perspective view of a rechargeable battery according to a first embodiment of the present invention, and  FIG. 2  is an exploded perspective view of the rechargeable battery shown in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a rechargeable battery  200  according an embodiment includes an electrode group  10 . The rechargeable battery may also include a positive electrode case  20 , a negative electrode case  30 , and a central case  40  that divide the electrode group  10  into three areas and that house the electrode group  10 . The positive electrode case  20  and the negative electrode case  30  may enclose one end portion and the opposite end portion of the electrode group  10 , respectively, and the central case  40  may enclose the entire central portion of the electrode group  10  and a part of the positive electrode case  20  and the negative electrode case  30 . 
     The electrode group  10  may be formed by winding in a jelly roll form. The electrode group  10  may be in a stack formed by folding in a zigzag method. The electrode group  10  may also be a stack of a positive electrode, a negative electrode, and a separator that are formed from a single plate.  FIG. 2  illustrates a stacked electrode group. In the electrode group  10 , the positive electrode  11  and the negative electrode  12  are alternately repeatedly stacked with a separator  13  interposed therebetween. The separator  13  may have a smaller width than the positive electrode  11  and the negative electrode  12 , and may be disposed at a predetermined distance from edges of the positive electrode  11  and the negative electrode  12 . 
     Thereby, a portion of the positive electrode  11  may be exposed to the outside of the separator  13  at one end portion of the electrode group  10 , and a portion of the negative electrode  12  may be exposed to the outside of the separator  13  at the other end portion of the electrode group  10 . The exposed portion of the positive electrode  11  may be a positive electrode uncoated portion  14  in which a positive electrode active material is not coated in a positive electrode current collector, and a portion of the exposed negative electrode  12  is a negative electrode uncoated portion  15  in which a negative electrode active material is not coated in a negative electrode current collector. 
     Therefore, the electrode groups  10  and  110  may be divided into a central portion  16  at which the separator  13  is positioned, the positive electrode uncoated portion  14  that is positioned at a one end portion of the central portion  16 , and the negative electrode uncoated portion  15  that is positioned at an opposite end portion of the central portion  16 . 
     Edges of the positive electrode uncoated portion  14  and the negative electrode uncoated portion  15 , respectively, may closely contact each other, for example, by pressing, and may be bonded, for example by welding. For convenience, respective portions that are disposed toward one point in the positive electrode uncoated portion  14  and the negative electrode uncoated portion  15  will be referred to as curve portions  141  and  151 , and respective bonded regions will be referred to as a positive electrode current collecting portion  142  and a negative electrode current collecting portion  152 . 
     The positive electrode current collecting portion  142  and the negative electrode current collecting portion  152  may be positioned at the center of the electrode group  10  in the direction of the thickness of the electrode group  10 , or may be positioned to one side of the electrode group  10  in the direction of the thickness of the electrode group  10 .  FIG. 2  illustrates the second case. 
       FIG. 3  is a cross-sectional view of the rechargeable battery of  FIG. 1 . 
     Referring to  FIGS. 1 and 3 , the positive electrode case  20  is coupled to the positive electrode current collecting portion  142  to be electrically connected thereto, and is integrally formed with a positive electrode terminal  21  that is protruded to the outside. The negative electrode case  30  may be coupled to the negative electrode current collecting portion  152  to be electrically connected thereto, and is integrally formed with a negative electrode terminal  31  that is protruded to the outside. The positive electrode case  20  and the negative electrode case  30  may each be formed with a hard metal having high electrical conductivity. 
     The positive electrode case  20  can include a first receiving portion  22  that encloses the curve portion  141  and a part of a central portion  16  toward the curve portion  141 , a second receiving portion  23  that is positioned at the outside of the first receiving portion  22  and that encloses the positive electrode current collecting portion  142 , and the positive electrode terminal  21  that is positioned at the outside of the second receiving portion  23 . The first receiving portion  22 , the second receiving portion  23 , and the positive electrode terminal  21  may be integrally connected. 
     The first receiving portion  22  may be formed in an approximately rectangular parallelepiped shape having one opened side surface, and a side surface thereof can include a linear portion  24  that is opposite to the central portion  16  and an inclined portion  25  that covers the curve portion  141 . 
     When the positive electrode current collecting portion  142  is positioned at the center of the electrode group  10  in a direction of the thickness of the electrode group  10 , each of the inclined portions  25  may be positioned at an upper part and a lower part of the curve portion  141 . Alternatively, when the positive electrode current collecting portion  142  is positioned at one side in a direction of the thickness of the electrode group  10 , one inclined portion  25  may be positioned at the outside of the curve portion  141 .  FIG. 2  illustrates the second case. 
     The second receiving portion  23  may form an internal space into which the positive electrode current collecting portion  142  is inserted. The positive electrode current collecting portion  142  may be fixed to the second receiving portion  23  by welding. For this purpose, the second receiving portion  23  can have at least one recess portion  26  and thus partially reduce a thickness thereof, and the second receiving portion  23  and the positive electrode current collecting portion  142  may be fixed by spot welding at the recess portion  26 . Two recess portions  26  may be formed symmetrical to each other at an upper surface and a lower surface of the second receiving portion  23 . 
     Therefore, the entire positive electrode case  20  including the positive electrode terminal  21  may be electrically connected to the positive electrode  11  by coupling of the second receiving portion  23  and the positive electrode current collecting portion  142 . In this way, the positive electrode case  20  can perform various functions as an input terminal, an output terminal, and a casing structure. 
     The negative electrode case  30  may have the same shape as that of the positive electrode case  20 , and a second receiving portion  33  and the negative electrode current collecting portion  152  may be integrally fixed by welding and thus the entire negative electrode case  30  including the negative electrode terminal  31  may be electrically connected to the negative electrode  12 . In  FIG. 3 , reference numeral  32  can indicate a first receiving portion of the negative electrode case  30 , and reference numerals  34  and  35  can indicate a linear portion and an inclined portion, respectively, of the first receiving portion  32 . Reference numeral  36  can indicate a recess portion of the second receiving portion  33 . 
     The central case  40  can enclose the entire central portion  16  of the electrode group  10  and portions of the first receiving portions  22  and  32  of the positive electrode case  20  and the negative electrode case  30 , and may be bonded to the positive electrode case  20  and the negative electrode case  30 . The central case  40  can be formed with a laminate sheet in which a metal layer and a resin layer are bonded by an adhesive layer. 
     The central case  40  may be bonded to an outer surface of the linear portions  24  and  34  of the positive electrode case  20  and the negative electrode case  30  by thermal bonding. In  FIG. 3 , reference numeral  41  can indicate a sealing portion of the positive electrode case  20  and the central case  40  and a sealing portion of the negative electrode case  30  and the central case  40 . 
     Therefore, the sealing portion  41  of the positive electrode case  20  and the central case  40  may correspond to the central portion  16  of the electrode group  10 , and may be positioned at the inside of a bonding portion of the positive electrode current collecting portion  142  and the second receiving portion  23 . The sealing portion  41  of the negative electrode case  30  and the central case  40  can also correspond to the central portion  16  of the electrode group  10 , and be positioned at the inside of a bonding portion of the negative electrode current collecting portion  152  and the second receiving portion  33 . 
     In the rechargeable battery  200  of the above-described structure, the sealing portion  41  of the cases  20 ,  30 , and  40  can be positioned at the inside of the positive electrode current collecting portion  142  and the negative electrode current collecting portion  152 , and the positive electrode terminal  21  and the negative electrode terminal  31  can be respectively positioned at the outside of the positive electrode current collecting portion  142  and the negative electrode current collecting portion  152 , and thus an outer portion width of the electrode group  10  that does not contribute to an actual battery reaction of the entire rechargeable battery  200  can be effectively reduced. 
     Therefore, by increasing battery capacity by increasing a width of the electrode group  10  to the size of the rechargeable battery, or by decreasing an outer portion width of the electrode group  10  to the size of the electrode group, a more compact rechargeable battery can be manufactured. Therefore, in the rechargeable battery  200  of the first embodiment, because spatial utility can be increased, it is advantageous for forming the rechargeable battery  200  to have high capacity and a compact size. 
     Furthermore, the central case  40  that may be formed with a laminate sheet need not have a bending portion. That is, instead of the central case  40 , the positive electrode case  20  and the negative electrode case  30  may have a bending portion (border portion of a linear portion and an inclined portion), and because the positive electrode case  20  and the negative electrode case  30  may be formed with a hard metal, the bending portion need not have an influence on strength of the cases. 
     Therefore, the central case  40  does not have a structural weakness due to deep drawing, and may have a thickness of 0.15 mm to 1 mm, preferably 0.2 mm to 0.5 mm, more than a common laminate sheet. Therefore, the rechargeable battery  200  of the first illustrated embodiment can embody a thick battery having an entire thickness of 10 mm or more, and can more securely protect the electrode group  10 , and can minimize damage due to an external impact or vibration by increasing structural stability. 
     In  FIGS. 1 and 2 , the positive electrode terminal  21  and the negative electrode terminal  31  can have at least one opening  27  and  37 . The openings  27  and  37  can couple a connection member (not shown), and the connection member may be used when forming a battery module by coupling several rechargeable batteries  200  in series or in parallel. 
       FIG. 4  is a cross-sectional view of a rechargeable battery according to a second embodiment of the present invention. 
     Referring to  FIG. 4 , a rechargeable battery  210  according to the second embodiment may have a configuration similar to the rechargeable battery of the first embodiment, except for a structure of coupling a positive electrode current collecting portion  142  to a second receiving portion  231  of a positive electrode case  201  using a conductive fastening member  50 , and coupling a negative, electrode current collecting portion  152  to a second receiving portion  331  of a negative electrode case  301 . In the second embodiment, the coupling can occur by a structure such as a rivet or a bolt, instead of a welding process. Like reference numerals designate like elements of the rechargeable battery of the first illustrated embodiment. 
     At least one of openings  28  and  38  that expose the positive electrode and negative electrode current collecting portions  142  and  152  may be formed in the second receiving portions  231  and  331  of the positive electrode and negative electrode cases  201  and  301 , respectively, and openings corresponding to the openings  28  and  38  of the second receiving portions  231  and  331  may also be formed in the positive electrode and negative electrode current collecting portions  142  and  152 , respectively. Thereby, the fastening members  50  can fix the positive electrode and negative electrode current collecting portions  142  and  152  to the positive electrode and negative electrode cases  201  and  301  by penetrating through the second receiving portion  231  and the positive electrode current collecting portion  142 , and by penetrating through the second receiving portion  331  and the negative electrode current collecting portion  152 , respectively. 
       FIG. 5  is a cross-sectional view of a rechargeable battery according to a third embodiment of the present invention. 
     Referring to  FIG. 5 , a rechargeable battery  220  according to the third embodiment has a configuration similar to the rechargeable battery of the first embodiment, except that first receiving portions  221  and  321  of positive electrode and negative electrode cases  202  and  302  are formed in a rectangular parallelepiped shape in which both side surfaces of the first receiving portions  221  and  321  are opened without inclined portions, and second receiving portions  232  and  332  are formed to be orthogonal to the first receiving portions  221  and  321  at the outside of the first receiving portions  221  and  321 . Like reference numerals designate like elements of the rechargeable battery of the first illustrated embodiment. 
     The first receiving portion  221  of the positive electrode case  202  encloses a part of a central portion  16  and an entire curve portion  141  of the electrode group  10 , and the second receiving portion  232  thereof is formed orthogonal to the first receiving portion  221  and the positive electrode terminal  21 . The second receiving portion  232  forms at least one opening  29  that exposes an positive electrode current collecting portion  142 , and in the opening  29 , the positive electrode current collecting portion  142  and the second receiving portion  232  may be fixed by spot welding. The negative electrode case  302  may be formed in the same shape and manner as that of the positive electrode case  202 . 
     A central case  401  can enclose the entire central portion  16  of the electrode group  10  and the first and second receiving portions  221  and  232  of the positive electrode case  202 , and the first and second receiving portions  321  and  332  of the negative electrode case  302 , and may be bonded by thermal bonding to the second receiving portions  232  and  332 . In this case, a sealing portion  411  of the positive electrode and negative electrode cases  202  and  302  and the central case  401  may be disposed at the same line as that of the positive electrode and negative electrode current collecting portions  142  and  152  in a direction of the thickness of the electrode group  10 . 
     In the rechargeable battery  220  according to the third illustrated embodiment, by increasing the thickness of the second receiving portions  232  and  332  and increasing an overlapping area of the central case  401  relative to the positive electrode case  202  and the negative electrode case  302 , structural stability of the rechargeable battery  220  can be improved. 
     While embodiments of this invention has been described, 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.