Abstract:
A secondary battery comprises: a plurality of cylindrical electrode assemblies, wherein each electrode assembly comprises a positive electrode plate and a negative electrode plate rolled together with a separator interposed between the positive electrode plate and the negative electrode plate; a can housing the plurality of electrode assemblies; a cap assembly sealing the can; a positive electrode tab coupled to the positive electrode plate in each electrode assembly; and a negative electrode tab coupled to the negative electrode plate in each electrode assembly, wherein a first plurality of positive electrode tabs is aligned along a first line when viewed in one direction, and wherein a first plurality of negative electrode tabs is aligned along a second line when viewed in the one direction.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/408,984, filed on Nov. 1, 2010, with the U.S. Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND 
       [0002]    Aspects of the present invention relate to a secondary battery. 
         [0003]    Secondary batteries include an electrode assembly formed by sequentially stacking a positive electrode plate, a negative electrode plate and a separator and winding the same in one direction, a can housing the cylindrical electrode assembly, and a cap plate sealing an open portion of the prismatic can to thereby form a bare cell. The secondary battery generally includes an electrode terminal insulated from the cap plate and serving one of electrodes in the secondary battery. The cap plate and the can may serve the other electrode in the secondary battery. 
         [0004]    In the secondary battery, the electrode assembly is wound and then housed into a can in a planar state. When the electrode assembly swells during repeated charge/discharge operations, both of the planar side surfaces of the electrode assembly also swell. 
         [0005]    Accordingly, the swelling of the electrode assembly may result in swelling of the can, specifically both side surfaces which have relatively large areas. 
         [0006]    In order to achieve the above and other aspects of the present invention, one embodiment of the present invention provides a secondary battery including a plurality of cylindrical electrode assemblies, which is capable of preventing a prismatic can from swelling. 
         [0007]    At least one of the above and other features and advantages may be realized by providing a secondary battery including a plurality of cylindrical electrode assemblies wound in a jelly-roll configuration, each having a positive electrode tab connected to a positive electrode plate, and a negative electrode tab connected to a negative electrode plate, a prismatic can housing the plurality of cylindrical electrode assemblies, center pins inserted into the plurality of cylindrical electrode assemblies and coupled to the bottom of the can, and a cap assembly sealing the prismatic can. 
         [0008]    In the secondary battery according to the embodiments, swelling of the prismatic can may be prevented by forming a plurality of cylindrical electrode assemblies wound in a jelly-roll configuration and housed in the prismatic can. 
       SUMMARY 
       [0009]    According to an embodiment of the invention, a secondary battery comprises a plurality of electrode assemblies, wherein each electrode assembly comprises a positive electrode plate and a negative electrode plate rolled together with a separator interposed between the positive electrode plate and the negative electrode plate. The secondary battery may comprise a can housing the plurality of electrode assemblies; a cap assembly sealing the can; a positive electrode tab coupled to the positive electrode plate in each electrode assembly; and a negative electrode tab coupled to the negative electrode plate in each electrode assembly. A first plurality of positive electrode tabs is aligned along a first line when viewed in one direction, and a first plurality of negative electrode tabs is aligned along a second line when viewed in the one direction. 
         [0010]    According to an aspect, the secondary battery further comprises a second plurality of positive electrode tabs aligned along a third line when viewed in the one direction. 
         [0011]    According to an aspect, the secondary battery further comprises a second plurality of negative electrode tabs aligned along a fourth line when viewed in the one direction. 
         [0012]    According to an aspect, the secondary battery further comprises a third plurality of positive electrode tabs aligned along a fifth line when viewed in the one direction. 
         [0013]    According to an aspect, the secondary battery further comprises a third plurality of negative electrode tabs aligned along a sixth line when viewed in the one direction. 
         [0014]    According to an aspect, the first plurality of positive electrode tabs is connected to a positive connection tab, and wherein the first plurality of negative electrode tabs is connected to a negative connection tab. 
         [0015]    According to an aspect, the first plurality of positive electrode tabs is connected to a first positive connection tab, the first plurality of negative electrode tabs is connected to a first negative connection tab, the second plurality of positive electrode tabs is connected to a second positive connection tab, and the second plurality of negative electrode tabs is connected to a second negative connection tab. 
         [0016]    According to an aspect, the first plurality of positive electrode tabs is connected to a first positive connection tab, the first plurality of negative electrode tabs is connected to a first negative connection tab, the second plurality of positive electrode tabs is connected to a second positive connection tab, the second plurality of negative electrode tabs is connected to a second negative connection tab, the third plurality of positive electrode tabs is connected to a third positive connection tab, and the third plurality of negative electrode tabs is connected to a third negative connection tab. 
         [0017]    According to an aspect, the first plurality of positive electrode tabs and the second plurality of positive electrode tabs are connected to a first positive connection tab. 
         [0018]    According to an aspect, the first plurality of negative electrode tabs and the second plurality of negative electrode tabs are connected to a first negative connection tab. 
         [0019]    According to an aspect, the third plurality of positive electrode tabs is connected to a second positive electrode tab, and the third plurality of negative electrode tabs is connected to a second negative connection tab. 
         [0020]    According to an aspect, the first plurality of positive electrode tabs and the first plurality of negative electrode tabs are coupled to a first plurality of electrode assemblies. 
         [0021]    According to an aspect, the second plurality of positive electrode tabs and the third plurality of negative electrode tabs are coupled to a second plurality of electrode assemblies. 
         [0022]    According to an aspect, the third plurality of positive electrode tabs and the second plurality of negative electrode tabs are coupled to a third plurality of electrode assemblies. 
         [0023]    According to an embodiment of the invention, a secondary battery comprises a plurality of electrode assemblies, a can housing the plurality of electrode assemblies, a cap assembly sealing the can, a positive electrode tab coupled to each electrode assembly, and a negative electrode tab coupled to each electrode assembly. The secondary battery may comprise a pin inserted in at least one electrode assembly, wherein the pin is coupled to the bottom surface of the can. A plurality of positive electrode tabs are aligned along a first line when viewed in one direction, and a plurality of negative electrode tabs are aligned along a second line when viewed in the one direction. 
         [0024]    According to an aspect, a bottom surface of the pin is welded to the bottom surface of the can. 
         [0025]    According to an aspect, the pin comprises a blade extending from a bottom portion of the pin, and the blade is welded to the bottom surface of the can. 
         [0026]    According to an aspect, a bottom portion of the pin is bent outwards, and the bent portion is welded to the bottom surface of the can. 
         [0027]    According to an aspect, a bottom portion of the pin is engaged with a protrusion formed on the bottom surface of the can. 
         [0028]    According to an aspect, the pin comprises a metallic material. According to an aspect, the pin comprises a plastic material. 
         [0029]    According to an aspect, the pin has a hollow and cylindrical shape. 
         [0030]    According to an aspect, the pin comprises a length in a range of approximately 90% to approximately 110% a total length of the electrode assembly. 
         [0031]    According to an aspect, the electrode assembly is cylindrical, and the pin is inserted into a center portion of the cylindrical electrode assembly. 
         [0032]    According to an aspect, the positive electrode tabs and the negative electrode tabs have major surfaces that face each other. 
         [0033]    According to an aspect, the cap assembly comprises an insulation case, and the positive electrode tabs and the negative electrode tabs are inserted through holes formed in the insulation case. 
         [0034]    According to an aspect, the cap assembly further comprises a cap plate, and the negative electrode tabs are electrically connected to electrode terminals positioned on an upper surface of the cap plate. 
         [0035]    According to an aspect, the positive electrode tabs are electrically connected to a lower surface of the cap plate. 
         [0036]    According to an aspect, the positive electrode tabs are electrically connected to an inner surface of the can. 
         [0037]    According to an aspect, the secondary battery further comprises a plurality of pins, wherein each pin is inserted in each of the electrode assemblies, and wherein each pin is coupled to the bottom surface of the can. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]      FIG. 1A  is an exploded perspective view of a secondary battery according to an embodiment of the present invention, and  FIG. 1B  is an enlarged view illustrating a portion “ 3 ” indicated by a dashed dot line in  FIG. 1A ; 
           [0039]      FIG. 2  is a sectional view taken along line  2 - 2 ′ in  FIG. 1A ; 
           [0040]      FIG. 3  is a vertical section view illustrating a portion corresponding to  FIG. 2  in a secondary battery according to another embodiment of the present invention; 
           [0041]      FIG. 4  is a vertical section view illustrating a portion corresponding to  FIG. 2  in a secondary battery according to another embodiment of the present invention; 
           [0042]      FIGS. 5A and 5B  are sectional views illustrating coupled states of the secondary battery shown in  FIG. 1A ; and 
           [0043]      FIG. 6A  is a front view illustrating a plurality of electrode assemblies inserted into a can of a secondary battery according to another embodiment of the invention, and  FIG. 6B  is a front view illustrating a plurality of electrode assemblies inserted into a can of a secondary battery according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    Embodiments will now be described more fully hereinafter with reference to the accompanying drawings. 
         [0045]      FIG. 1A  is an exploded perspective view of a secondary battery according to an embodiment of the present invention, and  FIG. 1B  is an enlarged view illustrating a portion “ 3 ” indicated by a dashed dot line in  FIG. 1A . 
         [0046]      FIG. 2  is a sectional view taken along line  2 - 2 ′ in  FIG. 1A . For clarity of description, it is noted that  FIG. 2  is obtainable when the electrode assemblies shown in  FIG. 1A  are rotated by 90 degrees. 
         [0047]    Referring to  FIG. 1A , the secondary battery  100  according to the illustrated embodiment includes a can  120 , a plurality of electrode assemblies  130 , center pins  140 , and a cap assembly  150 . 
         [0048]    In the secondary battery  100 , the plurality of cylindrical electrode assemblies  130  may be inserted into the prismatic can  120  through an upper open portion formed in the prismatic can  120 . The center pins  140  may be inserted into centers of the cylindrical electrode assemblies  130 , and may be fixed to the bottom of the can  120 . The can  120  may be sealed by the cap assembly  150 . 
         [0049]    The can  120  may include an opening  122 . The can  120  may have a substantially cuboid shape, and side edges thereof may be rounded. In addition, the can  120  may be made of a lightweight, conductive metal such as aluminum or an aluminum alloy, but aspects of the present invention are not limited thereto. In addition, the can  120  can function as an electrode terminal and may be a positive electrode. Preferably, the can  120  may be formed by deep drawing, but aspects of the present invention are not limited thereto. 
         [0050]    In addition, an electrolytic solution (not shown) may be injected into the can  120 , allowing lithium ions to move between positive and negative electrode plates, the lithium ions generated by an electrochemical reaction carried out in the battery during charge/discharge operations. The electrolytic solution (not shown) may be a non-aqueous organic electrolytic solution prepared by mixing a lithium salt and a high-purity organic solvent. In addition, the electrolytic solution (not shown) may be a polymer using a polymeric electrolyte, but is not limited thereto. 
         [0051]    The opening  122  may be formed on a top portion of the can  120 , the electrode assemblies  130  may be inserted into the can  120  through the opening  122 . The opening  122  may be sealed by the cap assembly  150 . 
         [0052]    The electrode assemblies  130  may include two or more unit electrode assemblies  130 . In an exemplary embodiment, the electrode assemblies  130  may include a first electrode assembly  132 , a second electrode assembly  134 , and third electrode assembly  136 . The first electrode assembly  132 , the second electrode assembly  134 , and the third electrode assembly  136  may be inserted into a single prismatic can  120  while being spaced apart from each other at minimum intervals. 
         [0053]    While three of the electrode assemblies  130  are illustrated herein, aspects of the present invention are not limited thereto and multiple electrode assemblies may be provided. 
         [0054]    The first electrode assembly  132  may include a first positive electrode tab  132   d  and a first negative electrode tab  132   e  electrically connected to a first positive electrode plate  132   a  and a first negative electrode plate  132   b , respectively. The second electrode assembly  134  may include a second positive electrode tab  134   d  and a second negative electrode tab  134   e  electrically connected to a second positive electrode plate  134   a  and a second negative electrode plate  134   b , respectively. In addition, the third electrode assembly  136  may include a third positive electrode tab  136   d  and a third negative electrode tab  136   e  electrically connected to a third positive electrode plate  136   a  and a third negative electrode plate  136   b , respectively. Here, the first positive electrode tab  132   d , the second positive electrode tab  134   d  and the third positive electrode tab  136   d  are electrically connected. In addition, the first negative electrode tab  132   e , the second negative electrode tab  134   e  and the third negative electrode tab  136   e  are also electrically connected. The first positive electrode tab  132   d , the second positive electrode tab  134   d  and the third positive electrode tab  136   d , and the first negative electrode tab  132   e , the second negative electrode tab  134   e  and the third negative electrode tab  136   e  are all formed to face the opening  122  of the can  120 . 
         [0055]    In addition, the first electrode assembly  132 , the second electrode assembly  134  and the third electrode assembly  136  may be electrically connected in parallel. 
         [0056]    Since the first electrode assembly  132 , the second electrode assembly  134  and the third electrode assembly  136  can have substantially the same configurations, the following description will focus on the first electrode assembly  132 . 
         [0057]    The first electrode assembly  132  includes a first positive electrode plate  132   a , a first negative electrode plate  132   b , and a first separator  132   c . The first electrode assembly  132  may be fabricated by stacking the first positive electrode plate  132   a  and the first negative electrode plate  132   b  with the first separator  132   c  interposed therebetween, and the resulting structure may be wound into a jelly roll configuration. 
         [0058]    The first positive electrode plate  132   a  can include a positive electrode collector formed of a highly conductive metal foil, for example, aluminum (Al) foil, and a positive electrode active material coated on a surface of the positive electrode collector. A portion of the positive electrode collector, where the positive electrode active material is not coated, that is, a positive electrode uncoated portion, may be formed at both ends of the first positive electrode plate  132   a , and the first positive electrode tab  132   d  made of Al may be welded to one side of the positive electrode uncoated portion. 
         [0059]    The first negative electrode plate  132   b  can include a negative electrode collector formed of a conductive metal foil, for example, copper (Cu) foil, and a negative electrode active material coated on a surface of the negative electrode collector. A portion of the negative electrode collector, where the negative electrode active material is not coated, that is, a negative electrode uncoated portion, may be formed at both ends of the first negative electrode plate  132   b , and the first negative electrode tab  132   e  made of nickel (Ni) may be welded to one side of the negative electrode uncoated portion. 
         [0060]    The first separator  132   c  is positioned between the first positive electrode plate  132   a  and the first negative electrode plate  132   b . The separator  132   c  may be formed of a porous film made of polyethylene (PE), polypropylene (PP), or a combination thereof, but aspects of the present invention are not limited thereto. 
         [0061]    The first separator  132   c  can inhibit electronic conduction in the first electrode assembly  132  with the first positive electrode plate  132   a  and the first negative electrode plate  132   b  and permit lithium ions to pass therebetween. 
         [0062]    The first separator  132   c  can inhibit the first positive electrode plate  132   a  and the first negative electrode plate  132   b  from contacting each other, and prevent the temperature of the secondary battery  100  from increasing by shutting down the flow of current when the temperature of the secondary battery  100  rises due to an external short. In order to prevent a short between the first positive electrode plate  132   a  and the first negative electrode plate  132   b , a ceramic layer prepared by mixing a ceramic material with a binder may further be provided in addition to the first separator  132   c.    
         [0063]    In addition, the first separator  132   c  is preferably wider than the first positive electrode plate  132   a  and the first negative electrode plate  132   b  in inhibiting a short between electrode plates. 
         [0064]    Each of the center pins  140  is shaped of a hollow cylinder. In addition, the length of the center pin  140  is preferably approximately  90  to approximately 110% of the total length of the first electrode assembly  132 . If the length of the center pin  140  is less than or equal to 90% of the total length of the first electrode assembly  132 , the first electrode assembly  132  can be fixed or supported in a weak state. Meanwhile, if the length of the center pin  140  is greater than or equal to 110% of the total length of the first electrode assembly  132 , the center pin  140  may not contact components of the cap assembly  150 , which is not desirable. 
         [0065]    The center pins  140  may be made of a metal. The center pins  140  are inserted into a space formed in the center of the first electrode assembly  132 . The center pins  140  may be welded to the bottom of the can  120 . The center pins  140  can support the first electrode assembly  132 , and suppress deformation and movement of the first electrode assembly  132  due to charge/discharge operations. In addition, since the center pins  140  are formed in the first electrode assembly  132 , the second electrode assembly  134  and the third electrode assembly  136 , respectively, it can inhibit each electrode assembly from moving due to a volumetric change. 
         [0066]    The cap assembly  150  may include a cap plate  151 , a gasket  152 , an electrode terminal  153 , an insulation plate  154 , a terminal plate  155 , an insulation case  156 , and a plug  157 . 
         [0067]    The cap assembly  150  may be sized and shaped corresponding to the opening  122  of the can  120 , and may be installed in the opening  122  of the can  120  to be sealed. 
         [0068]    The cap plate  151  may be a planar metal member sized and shaped corresponding to an entrance of the can  120 . The cap plate  151  may be coupled to the can  120  by, for example, welding, and can function as the same electrode as the can  120 , that is, a positive electrode. In order to facilitate welding, the can  120  and the cap plate  151  may be made of the same electrically conductive metal, such as aluminum or an aluminum alloy. An electrolyte injection hole  151   a  through which an electrolytic solution is injected may be formed at one side of the cap plate  151 . 
         [0069]    The first positive electrode tab  132   d , the second positive electrode tab  134   d , and the third positive electrode tab  136   d  are welded to the bottom surface of the cap plate  151  to then be electrically connected, so that the outside of the secondary battery  100 , excluding the electrode terminal  153 , can function as a positive electrode terminal. Here, the positive electrode tabs  132   d ,  134   d , and  136   d  may penetrate throughholes  156   a  formed in the insulation case  156 , respectively, which will later be described, and then be adhered to a bottom surface of the cap plate  151  after being bent if necessary. Alternatively, the first positive electrode tab  132   d , the second positive electrode tab  134   d , and the third positive electrode tab  136   d  may also be directly electrically connected to an inner surface of the can  120 . 
         [0070]    According to an embodiment, the gasket  152  is tubular and positioned on an outer surface of the electrode terminal  153 . The gasket  152  may insulate the electrode terminal  153  from the cap plate  151 . 
         [0071]    The electrode terminal  153  may be positioned at the cap assembly  150 , and extend through the cap plate  151  while surrounding the outer circumference surface of the gasket  152 . The first negative electrode plate  132   b , the second negative electrode tab  134   b , and the third negative electrode tab  136   b  may be electrically connected to the electrode terminal  153 , functioning as a negative electrode terminal. 
         [0072]    According to an embodiment, the insulation plate  154  is plate-shaped and positioned on the bottom surface of the cap plate  151 . The insulation plate  154  may be made of the same insulating material as the gasket  152 . Therefore, the cap plate  151  and the terminal plate  155  to be described later may be insulated from each other by the insulation plate  154 . 
         [0073]    The terminal plate  155  may be made of a metal and is positioned on the bottom surface of the insulation plate  154 . The electrode terminal  153  may be riveted by the terminal plate  155 , so that it may not be dislodged from the cap plate  151 . 
         [0074]    The first negative electrode tab  132   e , the second negative electrode tab  134   e , and the third negative electrode tab  136   e  may be directly welded to the terminal plate  155 , and the terminal plate  155  may be installed to be electrically conducted to the electrode terminal  153 , thereby allowing the electrode terminal  153  to function as a negative electrode terminal. Here, the negative electrode tabs  132   e ,  134   e , and  136   e  may penetrate the throughholes  156   a  formed in the insulation case  156 , respectively, which will later be described, and then be adhered to the bottom surface of the cap plate  151  after being bent if necessary. 
         [0075]    Meanwhile, the terminal plate  155  may not be provided, and accordingly, the first negative electrode tab  132   e , the second negative electrode tab  134   e , and the third negative electrode tab  136   e  may be directly connected to the electrode terminal  153 . 
         [0076]    According to an embodiment, the insulation case  156  is installed between the electrode assembly  130 , specifically the electrode assemblies  132 ,  134  and  136 , and the cap assembly  150  to prevent the electrode assemblies  132 ,  134  and  136  from moving up and down. In addition, the insulation case  156  may be installed to prevent the electrode assemblies  132 ,  134  and  136  from being directly shorted to the cap assembly  150 . In addition, the insulation case  156  can include a plurality of throughholes  156   a  and  156   b  to allow the positive electrode tabs  132   d ,  134   d , and  136   d  and the negative electrode tabs  132   e ,  134   e , and  136   e  to pass therethrough upwardly. Further, the electrolytic solution injected through the electrolyte injection hole  151   a  may be provided to the lower electrode assemblies  132 ,  134  and  136  via the throughholes  156   a  and  156   b  of the insulation case  156 . The insulation case  156  may be made of a polymeric resin having an insulating property, preferably, polypropylene. 
         [0077]    The plug  157  may be provided to seal the electrolyte injection hole  151   a  after the electrolytic solution is injected into the can  120  through the electrolyte injection hole  151   a . The plug  157  may be generally made of aluminum or an aluminum containing metal. The plug  157  may be mechanically pressed into the electrolyte injection hole  151   a  and then engaged with the electrolyte injection hole  151   a.    
         [0078]    A secondary battery  200  according to another embodiment of the present invention will now be described. 
         [0079]      FIG. 3  is a vertical section view illustrating a portion corresponding to  FIG. 2  in a secondary battery according to another embodiment of the present invention. 
         [0080]    The secondary battery  200  according to the illustrated embodiment of the present invention includes a can  120 , electrode assemblies  130 , center pins  240 , and a cap assembly  150 . 
         [0081]    Referring to  FIG. 1B , which is an enlarged view illustrating a portion “ 3 ” indicated by a dashed dot line in  FIG. 1A , main surfaces  132   f ,  134   f  and  136   f  of the plurality of positive electrode tabs  132   d ,  134   d  and  136   d  are formed to face main surfaces  132   h ,  134   h  and  136   h  of the plurality of negative electrode tabs  132   e ,  134   e  and  136   e . The main surfaces  132   f ,  134   f  and  136   f  of the plurality of positive electrode tabs  132   d ,  134   d  and  136   d  and the main surfaces  132   h ,  134   h  and  136   h  of the plurality of negative electrode tabs  132   e ,  134   e  and  136   e  face a main surface  120   a  of the can  120 . Narrow surfaces  132   g ,  134   g  and  136   g  of the plurality of positive electrode tabs  132   d ,  134   d  and  136   d  and narrow surfaces  132   i ,  134   i  and  136   i  of the plurality of negative electrode tabs  132   e ,  134   e  and  136   e  face a round surface  120   b  of the can  120 . 
         [0082]    The positive electrode tabs  132   d ,  134   d  and  136   d  are aligned along a line, which means that the negative electrode tabs  132   e ,  134   e  and  136   e  are not positioned along the line formed by the plurality of positive electrode tabs  132   d ,  134   d  and  136   d.    
         [0083]    The negative electrode tabs  132   e ,  134   e  and  136   e  may be positioned on a line different from the line along which the plurality of positive electrode tabs  132   d ,  134   d  and  136   d . That is to say, the plurality of positive electrode tabs  132   d ,  134   d  and  136   d  may not be positioned along the line formed by the plurality of negative electrode tabs  132   e ,  134   e  and  136   e.    
         [0084]      FIG. 5A  is a sectional view illustrating a coupled state of the secondary battery shown in  FIG. 1A . 
         [0085]    The plurality of positive electrode tabs  132   d ,  134   d  and  136   d  are connected to the cap plate  151 , respectively. The plurality of positive electrode tabs  132   d ,  134   d  and  136   d  may penetrate the throughholes  156   a  formed in the insulation case  156  to then be bent, respectively, and may be coupled to the bottom surface of the cap plate  151 . 
         [0086]    The plurality of negative electrode tabs  132   e ,  134   e  and  136   e  may penetrate the throughholes  156   b  formed in the insulation case  156  to then be bent, respectively, and may be coupled to the bottom surface of the terminal plate  155 . 
         [0087]      FIG. 5B  is a sectional view illustrating another example of a coupled state of the secondary battery shown in  FIG. 1A . 
         [0088]    The plurality of positive electrode tabs  132   d ,  134   d  and  136   d  may be stacked one on top of another to then be coupled to the cap plate  151 . The plurality of positive electrode tabs  132   d ,  134   d  and  136   d  may penetrate the throughholes  156   a  formed in the insulation case  156  to then be bent, respectively, and may be coupled to the bottom surface of the cap plate  151  in a state where they are stacked one on top of another. 
         [0089]    The plurality of negative electrode tabs  132   e ,  134   e  and  136   e  may penetrate throughholes  156   b  formed in the insulation case  156  to then be bent, respectively, and may be coupled to the bottom surface of the terminal plate  155  in a state where they are stacked one on top of another. 
         [0090]    The secondary battery  200  according to the present embodiment is substantially the same as the secondary battery  100  shown in  FIGS. 1 and 2 , except for the configurations of the center pins  240 . Thus, the following description will focus on the center pins  240 . In addition, since the can  120 , the electrode assemblies  130  and the cap assembly  150  of the secondary battery  200  according to the illustrated embodiment of the present invention are formed in the same manner as corresponding ones of the previous embodiment shown in  FIGS. 1 and 2 , they will be identified by the same reference numerals, and detailed descriptions thereof will be omitted. 
         [0091]    Referring to  FIG. 3 , each of the center pins  240  includes a blade  241  formed on its bottom surface. The blade  241  is formed such that the bottom of the center pin  240  is bent and faces outwardly. 
         [0092]    The center pin  240  may be made of a metal. The blade  241  of the center pin  240  may be welded to the bottom of the can  120 . Since the blade  241  contacts the bottom of the can  120  with an increasing contact area, the center pin  240  can be more effectively supported, thereby improving coupling reliability. 
         [0093]    A secondary battery according to another embodiment of the present invention will now be described.  FIG. 4  is a vertical section view illustrating a portion corresponding to  FIG. 2  in a secondary battery according to another embodiment of the present invention. 
         [0094]    The secondary battery  300  according to the illustrated embodiment includes a can  320 , electrode assemblies  130 , a center pin  340 , and a cap assembly  150 . 
         [0095]    The secondary battery  300  according to the present embodiment is substantially the same as the secondary battery  100  shown in  FIGS. 1 and 2 , except for configurations of the can  320  and the center pin  340 . Thus, the following description will focus on the can  320  and the center pin  340 . In addition, since the electrode assemblies  130  and the cap assembly  150  of the secondary battery  300  according to the illustrated embodiment of the present invention are formed in the same manner as corresponding ones of the previous embodiment shown in  FIGS. 1 and 2 , they will be identified by the same reference numerals, and detailed descriptions thereof will be omitted. 
         [0096]    Referring to  FIG. 4 , the can  320  may have protruding parts  321  formed at its bottom surface. The protruding parts  321  may have a size and height large enough for the bottom portion of the center pin  340  to be engaged with and fixed. In addition, the number of the protruding parts  321  may correspond to that of the center-pins  340 . Since the center pin  340  is directly engaged with each of the protruding parts  321 , it can reduce a welding process for fixedly welding the can  320  and the center pin  340  to each other. 
         [0097]    The center pin  340  may be shaped of a cylinder and made of a metallic or plastic material. 
         [0098]    A secondary battery according to yet another embodiment of the present invention will now be described. 
         [0099]      FIG. 6A  is a front view illustrating a plurality of electrode assemblies inserted into a can of a secondary battery according to yet another embodiment of the present invention. 
         [0100]    The secondary battery  400  according to the illustrated embodiment of the present invention includes a can  120 , electrode assemblies  130 , center pins  140 , a connection tab  460 , an insulation case (not shown), and a cap plate (not shown). 
         [0101]    In the illustrated secondary battery  400 , the electrode assemblies  130  are arranged in a manner different from those shown in  FIGS. 1A through 2 , and the connection tab  460  is additionally provided. Thus, the following description of the illustrated embodiment of the present invention will focus on the arranged state of the electrode assemblies  130  and the connection tab  460 . In addition, since the can  120 , the electrode assemblies  130 , the center pins  140 , the connection tab  460 , the insulation case (not shown) and the cap plate (not shown) of the illustrated secondary battery  400  are substantially the same as those of the previous embodiment shown in  FIGS. 1A through 2 , the same and corresponding functional components will be denoted by the same reference numerals and detailed descriptions thereof will not be given. 
         [0102]    At least three lines of the plurality of electrode assemblies  130  may be aligned in a row, respectively. The illustrated embodiment of the present invention does not limit the number of lines of the electrode assemblies  130  to that illustrated herein. 
         [0103]    The plurality of electrode assemblies  130  may be aligned such that a plurality of negative electrode tabs  432   e ,  432   g  and  432   i  are aligned above the respective center pins  140  while a plurality of positive electrode tabs  432   d ,  432   f  and  432   h  are aligned below the respective center pins  140 . Therefore, the positive electrode tabs  432   d  of the electrode assemblies  130  positioned on the first line and the negative electrode tabs  462   g  of the electrode assemblies  130  positioned on the second line alternately face each other. 
         [0104]    The connection tab  460  may include negative electrode connection tabs  460   a ,  460   c  and  460   e  and positive electrode connection tabs  460   b ,  460   d  and  460   f . The connection tab  460  may be shaped of a substantially rectangular plate. The connection tab  460  may be positioned on the insulation case (not shown). Here, the connection tab  460  can extend through the negative electrode connection tabs  460   a ,  460   c  and  460   e , the positive electrode connection tabs  460   b ,  460   d  and  460   f , and the insulation case (not shown) to be connected with the cap plate and terminal plate (?). 
         [0105]    Specifically, the positive electrode connection tabs  460   b ,  460   d  and  460   f  may be connected to the positive electrode tabs  432   d ,  432   f  and  432   h , and the negative electrode connection tabs  460   a ,  460   c  and  460   e  are connected to the negative electrode tabs  432   e ,  432   g  and  432   i . The positive electrode connection tabs  460   b ,  460   d  and  460   f  and the positive electrode tabs  432   d ,  432   f  and  432   h  may be connected to each other to then be connected to the cap plate (not shown). The negative electrode connection tabs  460   a ,  460   c  and  460   e  and the negative electrode tabs  432   e ,  432   g  and  432   i  may be connected to each other to then be connected to the terminal plate (not shown). 
         [0106]    In the present embodiment, the number of the connection tab  460  formed is six (6) in total. That is to say, each three connection tabs are formed, including three of the negative electrode connection tabs  460   a ,  460   c  and  460   e  and three of the positive electrode connection tabs  460   b ,  460   d  and  460   f . However, the illustrated embodiment of the present invention does not limit the number of the connection tab  460  to that illustrated herein. 
         [0107]    A secondary battery according to another embodiment of the present invention will now be described. 
         [0108]      FIG. 6B  is a front view illustrating a plurality of electrode assemblies inserted into a can of a secondary battery according to another embodiment of the present invention. 
         [0109]    The secondary battery  500  according to the illustrated embodiment of the present invention includes a can  120 , electrode assemblies  130 , center pins  140 , a connection tab  560 , an insulation case (not shown), and a cap plate (not shown). 
         [0110]    In the illustrated secondary battery  500 , the electrode assemblies  130  are arranged in a different manner from those shown in  FIGS. 1A through 2 , and the connection tab  560  is additionally provided. Thus, the following description of the illustrated embodiment of the present invention will focus on the arranged state of the electrode assemblies  130  and the connection tab  460 . In addition, since the can  120 , the electrode assemblies  130 , the center pins  140 , the connection tab  560 , the insulation case (not shown) and the cap plate (not shown) of the illustrated secondary battery  500  are substantially the same as those of the previous embodiment shown in  FIGS. 1A through 2 , the same and corresponding functional components will be denoted by the same reference numerals and detailed descriptions thereof will not be given. 
         [0111]    At least three lines of the plurality of electrode assemblies  130  may be aligned in a row. However, the illustrated embodiment of the present invention does not limit the number of lines of the electrode assemblies  130  to that illustrated herein. 
         [0112]    The plurality of electrode assemblies  130  may be aligned such that positive electrode tabs  532   f  and negative electrode tabs  532   g  of the second line are aligned opposite to positive electrode tabs  532   d  and  532   h  and negative electrode tabs  532   e  and  532   i  of the first and third lines in view of the respective center pins  140 . 
         [0113]    Therefore, the positive electrode tabs  532   d  of the electrode assemblies  130  positioned on the first line and the positive electrode tabs  532   f  of the electrode assemblies  130  positioned on the second line alternately face each other. 
         [0114]    The connection tab  560  may include positive electrode connection tabs  560   b  and  560   d  and negative electrode connection tabs  560   a  and  560   c . The connection tab  560  may be shaped of a substantially rectangular plate. The connection tab  560  may be positioned on the insulation case (not shown). Here, the connection tab  560  may extend through the positive electrode tabs  532   d ,  532   f  and  532   h  and the negative electrode tabs  532   e ,  532   g  and  532   i , and the insulation case (not shown) to be connected with the cap plate and terminal plate. 
         [0115]    Specifically, the positive electrode connection tabs  560   b  and  560   d  may be connected to the positive electrode tabs  532   d ,  532   f  and  532   h , and the negative electrode connection tabs  560   a  and  560   c  may be connected to the negative electrode tabs  532   e ,  532   g  and  532   i.    
         [0116]    The positive electrode connection tabs  560   b  and  560   d  and the positive electrode tabs  532   d ,  532   f  and  532   h  may be connected to each other to then be connected to the cap plate (not shown). The negative electrode connection tabs  560   a  and  560   c  and the negative electrode tabs  532   e ,  532   g  and  532   i  may be connected to each other to then be connected to the terminal plate (not shown). 
         [0117]    The number of the connection tab  560  formed may be four (4) in total. That is to say, each two connection tabs are formed, including two of the positive electrode connection tabs  560   b  and  560   d  and two of the negative electrode connection tabs  560   a  and  560   c . However, the illustrated embodiment of the present invention does not limit the number of the connection tab  560  to that illustrated herein. 
         [0118]    The plurality of electrode assemblies  130  may be aligned such that the positive electrode tabs  532   f  and the negative electrode tabs  532   g  of the second line are aligned opposite to the positive electrode tabs  532   d  and  532   h  and the negative electrode tabs  532   e  and  532   i  of the first and third lines in view of the respective center pins  140 , so that corresponding parts of the electrode assemblies  130  have the same polarity, thereby reducing the number of the connection tab  560 . 
         [0119]    While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.