Abstract:
An electrode assembly for a secondary battery and a method of manufacturing the same are disclosed. An electrode assembly comprises: a plurality of separator members formed by winding a central separator member, wherein the central separator member is a predeterminated portion of the separator; and a plurality of electrode members positioned between each of the separator members; wherein the separator including the plurality of separator members and the central separator member is one of the plurality of separator members, and wherein both opposite ends of the central separator member is curved in opposite directions, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Application No. 61/257,368, filed on Nov. 2, 2009, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to an electrode assembly for a secondary battery and a method of manufacturing the same. 
         [0004]    2. Description of the Related Technology 
         [0005]    A secondary battery is generally manufactured by accommodating an electrode assembly having a positive electrode plate, a negative electrode plate, and a separator interposed therebetween into an exterior case together with an electrolyte. 
         [0006]    In a high capacity secondary battery, a wound electrode assembly including a plurality of unit electrodes and separators may be used. In the wound electrode assembly, in a case where the number of turns of winding increases, it is not easy to accurately align the unit electrodes with the separators interposed therebetween. 
       SUMMARY 
       [0007]    According to an aspect of the present invention, an electrode assembly comprises: a plurality of separator members formed by winding a central separator member, wherein the central separator member is a predetermined portion of the separator; and a plurality of electrode members positioned between each of the separator members; wherein the separator including the plurality of separator members and the central separator member is one of the plurality of separator members, and wherein both opposite ends of the central separator member is curved in opposite directions, respectively. 
         [0008]    According to another aspect of the present invention, a secondary battery includes the electrode assembly having the above-described configuration. 
         [0009]    According to still another aspect of the present invention, a method of forming an electrode assembly comprises: forming a plurality of electrode members aligned in a first direction on a separator; forming a plurality of first and second electrode members on both surfaces of separator, respectively; and winding the separator from a central separator member to form a plurality of separator members interposed between the electrode members; wherein the central separator is predetermined portion of the separator, and wherein winding comprises both opposite ends of the central separator member is curved in opposite directions, respectively. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view illustrating a secondary battery including an electrode assembly according to an embodiment of the present invention; 
           [0011]      FIG. 2  is a schematic view illustrating an electrode assembly in  FIG. 1 ; 
           [0012]      FIG. 3  is a view illustrating a manufacturing process of the electrode assembly in  FIG. 2 ; 
           [0013]      FIG. 4  is a schematic view illustrating an electrode assembly according to another embodiment of the present invention; 
           [0014]      FIG. 5  is a view illustrating a manufacturing process of the electrode assembly in  FIG. 4 ; 
           [0015]      FIG. 6A  is a schematic view illustrating a modification of a first electrode of the electrode assembly shown in  FIG. 2 ; 
           [0016]      FIG. 6B  is a schematic view illustrating a modification of a second electrode of the electrode assembly shown in  FIG. 2 ; 
           [0017]      FIG. 7  is a schematic view illustrating another modification of the electrode assembly shown in  FIG. 1 ; and 
           [0018]      FIG. 8  is a schematic view illustrating still another modification of the electrode assembly shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    As illustrated in  FIGS. 1 to 7 , a battery pack  100  according to an embodiment of the present invention can include a bare cell  110 , a protective circuit module  120  electrically connected to the bare cell  110  to control the charge and discharge of the bare cell  110 , a first lead plate  130  and a second lead plate  140  supporting the protective circuit module  120  and electrically connecting the bare cell  110  to the protective circuit module  120 , and a cover  150  surrounding the bare cell  110  and the protective circuit module  120 . 
         [0020]    Hereinafter, embodiments of the present invention will be described in detail with reference accompanying drawings. 
         [0021]      FIG. 1  is a perspective view illustrating a secondary battery including an electrode assembly according to an embodiment of the present invention. Referring to  FIG. 1 , the secondary battery  10  is a pouch type secondary battery and includes a pouch case  20  and an electrode assembly  100  to be accommodated in the pouch case  20 . 
         [0022]    The pouch case  20  can include a body  22  and a cover  24 . The body  22  can include an accommodating portion  22   a  to accommodate the electrode assembly  100  and a sealing portion  23  extending to the outside of the accommodating portion  22   a . The cover  24  can be integrally coupled to one side of the sealing portion  23 . After the electrode assembly  100  is accommodated in the accommodating portion  22   a  of the body  22 , the body  22  and the cover  24  can contact each other closely and the sealing portion  23  can then be thermally welded. 
         [0023]      FIG. 2  is a schematic view illustrating the electrode assembly in  FIG. 1 . Referring to  FIGS. 1 and 2 , the electrode assembly  100  may include a separator  110  and a plurality of electrodes  120 . 
         [0024]    The separator  110  may be wound in one direction in view of a central portion  111   a  in a longitudinal direction and have a constant width, that is, clockwise when viewed from the drawing, which corresponds to a winding core. The wound separator  110  may include a plurality of stacked separator members  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f ,  111   g ,  111   h ,  111   i ,  111   j , and  111   k  with the winding core  111   a  positioned innermost. Each of a plurality of electrodes  120  may be positioned between each of the plurality of stacked separator members  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f ,  111   g ,  111   h ,  111   i ,  111   j , and  111   k . Opposite ends  1111   a  and  1112   a  of the central separator member corresponding to the winding core  111   a  may be bent in opposite directions to then be connected to the separator members  111   b  and  111   g  facing the central separator member  111   a . Longitudinally opposite ends  112   a  and  112   b  may be attached to the outer circumferential surface of the separator  110  using adhesive tapes  113  and  114 . The separator  110  may have a plurality of micropores allowing lithium ions migrating between the electrodes  120  to pass. The separator  110  may be made of a polymer such as polyethylene (PE) or polypropylene (PP). 
         [0025]    The plurality of electrodes  120  may be positioned one by one between each of the separator members  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f ,  111   g ,  111   h ,  111   i ,  111   j , and  111   k  of the separator  110 . The plurality of electrodes  120  may be arranged such that cores of two neighboring electrodes  120  are positioned at the same position with the separator  110  interposed therebetween. Accordingly, all of the plurality of electrodes  120  may be accurately aligned in a direction perpendicular to the separator members  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f ,  111   g ,  111   h ,  111   i ,  111   j , and  111   k . The electrodes  130   a  and  140   a  positioned at opposite sides of the central separator member  111   a  may be attached to both surfaces of the central separator member  111   a , and the remaining electrodes  130   b ,  130   c ,  130   d ,  130   e ,  140   b ,  140   c ,  140   d , and  140   e  may be attached to the inner surface of the central separator member  111   a.    
         [0026]    The electrodes  120  can include a plurality of first electrode members  130   a ,  130   b ,  130   c ,  130   d , and  130   e  and a plurality of second electrode members  140   a ,  140   b ,  140   c ,  140   d , and  140   e . The first electrode members  130   a ,  130   b ,  130   c ,  130   d , and  130   e  and the second electrode members  140   a ,  140   b ,  140   c ,  140   d , and  140   e  may be alternatively positioned. 
         [0027]    Each of the first electrode members  130   a ,  130   b ,  130   c ,  130   d , and  130   e  can include a positive electrode plate  131 . The positive electrode plate  131  can include a positive electrode collector  132  and positive electrode active materials  133  coated on both sides of the positive electrode collector  132 . The positive electrode collector  132  may generally be formed as a plate made of an electrically conductive metal such as aluminum. The positive electrode collector  132  may have a positive electrode tab  132   a  protruded outwardly without the positive electrode active material  133 . The positive electrode tab  132   a  of the positive electrode plate  131  may be welded to a positive terminal  160  protruded to the outside of the pouch case  20  by ultrasonic or resistance welding. The positive electrode active material  133  can include a layered lithium compound, an electrically conductive material to increase electric conductivity, and a binder to increase a binding force between the layered compound and the conductive material. 
         [0028]    Each of the second electrode members  140   a ,  140   b ,  140   c ,  140   d , and  140   e  can include a negative electrode plate  141 . The negative electrode plate  141  can include a negative electrode collector  142  and negative electrode active materials  143  coated on both sides of the negative electrode collector  142 . The negative electrode collector  142  may generally be formed as a plate made of an electrically conductive metal, such as copper. The negative electrode collector  142  can have a negative electrode tab  142   a  protruded outwardly without the negative electrode active material  143 . The negative electrode tab  142   a  of the respective negative electrode plates  141  may be welded to a negative terminal  170  protruded to the outside of the pouch case  20  by ultrasonic or resistance welding. The negative electrode active material  143  may be prepared by mixing a carbon material such as graphite and a binder to increase the binding force between carbon particles. In this case, the positive electrode plate may have an area smaller than that of the negative electrode plate. Further, when tin oxide (SnO) or lithium titanium oxide (LTO) is used as the negative electrode active material, the corresponding positive electrode plate may have an area larger than that of the negative electrode plate. 
         [0029]      FIG. 3  shows a process for manufacturing the electrode assembly shown in  FIG. 2 . Referring to  FIG. 3 , the separator  110 , which can include the first electrode members  130   a ,  130   b , and  130   c  and the second electrode members  140   a ,  140   b , and  140   c , is wound about a winding position P centrally positioned in a longitudinal direction. The first electrode member  130   a  and the second electrode member  140   a  may be disposed at equal positions on both surfaces of the separator  110  about the winding position P. Here, the central separator member  111   a  may be positioned at the winding position P. At one side of the winding position P, the first electrode members  130   b  and  130   c  may be linearly arranged on the same surface as the first electrode member  130   a . At the other side, which is opposite to the side of the winding position P, the second electrode members  140   b  and  140   c  may be linearly arranged on the same surface as the second electrode member  140   a . A distance D 1  between the first electrode member  130   a  may be positioned at the winding position P, and the first electrode member  130   b  arranged next to the first electrode member  130   a  may be adjusted such that the first electrode member  130   a  is covered by the separator member  111   g  formed between the first electrode members  130   a  and  130   b  in the separator  110 . In addition, a distance D 2  between the second electrode member  140   a  positioned at the winding position P and the second electrode member  140   b  arranged next to the second electrode member  140   a  may be adjusted such that the second electrode member  140   a  is covered by the separator member  111   b  formed between the second electrode members  140   a  and  140   b  in the separator  110 . Winding may be performed in a direction as shown in  FIG. 3  on the first electrode members  130   b  and  130   c  and the second electrode members  140   b  and  140   c , except for on the first electrode member  130   a  and the second electrode member  140   a  which would be positioned inside the wound assembly at the winding position P. The plurality of electrode members  130   a ,  130   b ,  130   c ,  140   a ,  140   b  and  140   c  may be added during the winding, and the distance between each of the electrodes  130  may be easily adjusted to achieve accurate alignment of the electrodes  130  during the winding. In other words, the electrodes  130  can be added to the separator  110  such that the distance between each of the electrodes  130  gradually increases as the winding continues. Thus, the plurality of electrode members  130   a ,  130   b ,  130   c ,  140   a ,  140   b  and  140   c  may be aligned at accurate positions. 
         [0030]      FIG. 4  is a schematic view of an electrode assembly according to another embodiment of the present invention. 
         [0031]    Referring to  FIG. 4 , the electrode assembly  200  can include a separator  210  and a plurality of electrode members  220 . Because the configuration and operation of the separator  210  may be identical to those of the separator  110  according to the previous embodiment shown in  FIG. 2 , detailed descriptions thereof will be omitted. 
         [0032]    Each of the plurality of electrode members  220  may be positioned between each of a plurality of separator members  211   a ,  211   b ,  211   c ,  211   d ,  211   e ,  211   f ,  211   g ,  211   h ,  211   i ,  211   j , and  211   k  of the separator  210 . The plurality of electrode members  220  may be arranged such that the centers of two neighboring electrode members of the plurality of electrode members  220  are aligned at the same position as the separator  210  interposed therebetween. For example, electrode members  230   a  and  240   a  of the plurality of electrode members  220 , positioned at opposite sides of a central separator member  211 , may be attached to both surfaces of the central separator member  211   a , and the other electrode members  230   b ,  230   c ,  230   d ,  230   e ,  240   b ,  240   c ,  240   d , and  240   e  may be attached to outer surfaces  210   b  of the separator  210 . Because the other structures and operations of the electrode assembly  200  may be identical to those of the electrode assembly  100  according to the previous embodiment shown in  FIG. 2 , detailed descriptions thereof will be omitted. 
         [0033]    A process of manufacturing the electrode assembly as shown in  FIG. 4  is illustrated in  FIG. 5 . 
         [0034]    Referring to  FIG. 5 , the separator  210 , which includes the first electrode members  230   a ,  230   b , and  230   c  and the second electrode members  240   a ,  240   b , and  240   c , may be wound in a longitudinal direction about a centrally positioned winding position P. The first electrode member  230   a  and the second electrode member  240   a  may be disposed at the same position, the winding position P, on both surfaces of the separator  210  At one side of the winding position P, the first electrode members  230   b  and  230   c  may be linearly arranged on the same surface as the first electrode member  230   a . At the other opposite side of the winding position P, the second electrode members  240   b  and  240   c  may be linearly arranged on the same surface as the second electrode member  240   a . Winding may be performed in a direction as shown in  FIG. 5  on the first electrode members  230   b  and  230   c  and on the second electrode members  240   b  and  240   c , except for on the first electrode member  230   a  and the second electrode member  240   a  which would be positioned inside the wound assembly at the winding position P. 
         [0035]      FIGS. 6A and 6B  illustrate a first electrode and a second electrode according to another embodiment of the present invention, respectively. 
         [0036]    Referring to  FIG. 6A , the first electrode  330  can include two positive electrode plates  331  and  332 , a single negative electrode plate  333  positioned between the positive electrode plates  331  and  332 , and two separators  334  and  335  respectively inserted between the negative electrode plate  333  and the positive electrode plate  331  and between the negative electrode plate  333  and the positive electrode plate  332 . Because the two positive electrode plates  331  and  332  may be identical to the positive electrode plate  131  as shown in  FIG. 2 , and the negative electrode plate  333  may be identical to the negative electrode plate  141  as shown in  FIG. 2 , detailed descriptions thereof will be omitted. Micropores may be formed in the separators  334  and  335 , and lithium ions migrating between the electrode plates  331 ,  332 , and  333  can pass through the micropores. The separators  334  and  335  may be formed of a polymer, such as polyethylene (PE) or polypropylene (PP). 
         [0037]    Referring to  FIG. 6B , the second electrode  340  can include two negative electrode plates  341  and  342 , a single positive electrode plate  343  positioned between the negative electrode plates  341  and  342 , and two separators  344  and  345  respectively inserted between the negative electrode plate  333  and the positive electrode plate  331  and between the negative electrode plate  333  and the positive electrode plate  332 . Since the two negative electrode plates  341  and  342  may be identical to the negative electrode plate  141  as shown in  FIG. 2  and the positive electrode plate  343  may be identical to the positive electrode plate  131  as shown in  FIG. 2 , detailed descriptions thereof will be omitted. Micropores may be formed in the separators  344  and  345 , and lithium ions migrating between the electrode plates  341 ,  342 , and  343  pass through the micropores. The separators  344  and  345  may be made of a polymer, such as polyethylene (PE) or polypropylene (PP). 
         [0038]    In the embodiment of  FIGS. 6A and 6B , each of the first and second electrodes may be formed by three electrode plates, but embodiments of the present invention are not limited thereto. That is, the first and second electrodes may be formed by more than three electrode plates. Alternatively, any structure may be employed, wherein electrode plates having different polarities are alternatively positioned and electrode plates having the same polarities are positioned opposite to each other. 
         [0039]      FIG. 7  is a schematic view illustrating another modification of the electrode assembly shown in  FIG. 1 . 
         [0040]    Referring to  FIG. 7 , the electrode assembly  400  can include a separator  410  and a plurality of electrode members  420   a ,  420   b ,  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j.    
         [0041]    Since structures and operations of the separator  410  may be identical to those of the separator  110 , detailed descriptions thereof will be omitted. 
         [0042]    Each of the plurality of electrode members  420   a ,  420   b ,  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j  may be positioned between each of a plurality of separator members  411   a ,  411   b ,  411   c ,  411   d ,  411   e ,  411   f ,  411   g ,  411   h ,  411   i ,  411   j , and  411   k  of the separator  410 . The plurality of electrode members  420   a ,  420   b ,  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j  may be arranged such that centers of two neighboring electrode members are aligned at the same position with the separator  410  interposed therebetween. For example, electrode members  420   a  and  420   b  positioned at opposite sides of a central separator member  411   a  may be attached to both surfaces of the central separator member  411   a , and the other electrode members  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j  may be attached to inner surfaces  410   b  of the separator  410 . 
         [0043]    Each of the plurality of electrode members  420   a ,  420   b ,  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j  can include a positive electrode plate  422  and a negative electrode plate  423  formed at opposite sides of a separator  421  interposed therebetween. Micropores may be formed in the separator  421 , and lithium ions migrating between the electrode plates  422  and  423  can pass through the micropores. The separator  421  may be made of a polymer, such as polyethylene (PE) or polypropylene (PP). The positive electrode plate  422  may be identical to the positive electrode plate  131  as shown in  FIG. 2 , and the negative electrode plate  423  may be identical to the negative electrode plate  141  as shown in  FIG. 2 . Thus, detailed descriptions thereof will be omitted. The electrode members  420   a ,  420   b ,  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j  may be formed such that electrode plates having different polarities face each other with the separator  410  interposed therebetween. 
         [0044]    The electrode assembly  400  shown in  FIG. 7  may be manufactured by arranging the plurality of electrode members  420   a ,  420   b ,  420   c ,  420   d ,  420   e ,  420   f ,  420   g ,  420   h ,  420   i , and  420   j  in the same manner as shown in  FIG. 3 , and winding the same. 
         [0045]      FIG. 8  is a schematic view illustrating still another modification of the electrode assembly shown in  FIG. 1 . 
         [0046]    Referring to  FIG. 8 , the electrode assembly  500  can include a separator  510  and a plurality of electrode members  520   a ,  520   b ,  520   c ,  520   d ,  520   e ,  520   f ,  520   g ,  520   h ,  520   i , and  520   j.    
         [0047]    Since structures and operations of the separator  510  may be identical to those of the separator  110 , detailed descriptions thereof will be omitted. 
         [0048]    Each of the plurality of electrode members  520   a ,  520   b ,  520   c ,  520   d ,  520   e ,  520   f ,  520   g ,  520   h ,  520   i , and  520   j  may be positioned between each of a plurality of separator members  511   a ,  511   b ,  511   c ,  511   d ,  511   e ,  511   f ,  511   g ,  511   h ,  511   i ,  511   j , and  511   k  of the separator  510 . The plurality of electrode members  520   a ,  520   b ,  520   c ,  520   d ,  520   e ,  520   f ,  520   g ,  520   h ,  520   i , and  520   j  may be arranged such that centers of two neighboring electrode members are aligned at the same position with the separator  510  interposed therebetween. For example, electrode members  520   a  and  520   b  positioned at opposite sides of a central separator member  511   a  may be attached to both surfaces of the central separator member  511   a , and the other electrode members  520   c ,  520   d ,  520   e ,  520   f ,  520   g ,  520   h ,  520   i , and  520   j  may be attached to outer surfaces  510   b  of the separator  510 . Because the other structures and operations of the electrode assembly  500  may be identical to those of the electrode assembly  400  according to the previous embodiment shown in  FIG. 7 , detailed descriptions thereof will be omitted. 
         [0049]    The electrode assembly  500  shown in  FIG. 8  may be manufactured by arranging the plurality of electrode members  520   a ,  520   b ,  520   c ,  520   d ,  520   e ,  520   f ,  520   g ,  520   h ,  520   i , and  520   j  in the same manner as shown in  FIG. 5 , and winding the same. 
         [0050]    As described above, since the winding of the separator can start from its central portion, rather than its terminal portion, the number of turns of winding can be reduced by half, compared to a case when the winding starts from the terminal portion of the separator. Further, since the electrode members positioned at opposite sides with the separator interposed therebetween can be wound in a symmetrical manner, the plurality of electrode members formed on the separator can be accurately aligned. 
         [0051]    Although embodiments of the present invention have been described in detail herein, it should be understood that many variations and modifications of the inventive concepts herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of embodiments of the present invention as defined in the appended claims.