Abstract:
A secondary battery including an electrode assembly wound about an axis extending in a first direction and including a coating portion having an active material thereon, and a non-coating portion at a first end of the electrode assembly along the first direction; a can containing the electrode assembly; a cap plate sealing an opening of the can; a terminal protruding outside the can; and a flexible current collector electrically connected between the non-coating portion of the electrode assembly and the terminal.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/435,665, filed on Jan. 24, 2011 in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Aspects of embodiments of the present invention relate to a secondary battery. 
         [0004]    2. Description of the Related Art 
         [0005]    Secondary batteries, unlike primary batteries, are rechargeable. Low-capacity secondary batteries are widely used in high-tech electronic devices such as cellular phones, notebook computers, and camcorders. High-capacity secondary batteries are widely used as motor-driving power sources of electric vehicles or hybrid vehicles. 
         [0006]    In general, such a secondary battery includes an electrode assembly disposed in a can, collectors, and electrode terminals. As secondary batteries are used in electric vehicles or hybrid vehicles, it is necessary to increase the capacities of the secondary batteries by efficiently using the inner spaces of the secondary batteries, and also to protect electrode assemblies of the secondary batteries from external impacts to increase reliability. 
       SUMMARY 
       [0007]    According to an aspect of embodiments of the present invention, a secondary battery has an inside space which can be optimally used to prevent or substantially prevent a short circuit of an electrode assembly caused by an impact and increase flexibility in component selection and disposition. 
         [0008]    According to an embodiment of the present invention, a secondary battery includes: an electrode assembly wound about an axis extending in a first direction and including a coating portion having an active material thereon, and a non-coating portion at a first end of the electrode assembly along the first direction; a can containing the electrode assembly; a cap plate sealing an opening of the can; a terminal protruding outside the can; and a flexible current collector electrically connected between the non-coating portion of the electrode assembly and the terminal. 
         [0009]    In one embodiment, a first end of the flexible current collector is coupled to the non-coating portion, and a second end of the flexible current collector is coupled to the terminal. The first end of the flexible current collector may be movable relative to the second end of the flexible current collector. 
         [0010]    The flexible current collector may include aluminum or copper. In one embodiment, the flexible current collector includes at least one wire. The at least one wire includes a plurality of wires that are twisted together along a length of the flexible current collector. 
         [0011]    In one embodiment, a secondary battery further includes an insulation member between the cap plate and the terminal. The insulation member may be between and contacting the can and the first end of the electrode assembly in the first direction. The insulation member may fix the electrode assembly from movement in the can. 
         [0012]    In one embodiment, a secondary battery further includes another electrode assembly in the can, the another electrode assembly including a coating portion having an active material thereon, and a non-coating portion at an end of the another electrode assembly along the first direction. The secondary battery may further include another flexible current collector electrically connected between the non-coating portion of the another electrode assembly and the terminal. In one embodiment, the secondary battery further includes an insulation member between the cap plate and the terminal, and the insulation member fixes the electrode assembly and the another electrode assembly from movement in the can. The flexible current collector and the another flexible current collector may respectively connect the electrode assembly and the another electrode assembly to the terminal in parallel to each other. 
         [0013]    In one embodiment, the electrode assembly further includes another non-coating portion at a second end of the electrode assembly opposite the first end, and the secondary battery further includes another terminal protruding outside the can, and another flexible current collector electrically connected between the another non-coating portion of the electrode assembly and the another terminal. 
         [0014]    In one embodiment, the flexible current collector has a substantially circular cross-sectional shape. In one embodiment, the flexible current collector has a substantially flat shape. The flexible current collector may be coupled to the non-coating portion by ultrasonic welding. The flexible current collector may be coated with a material selected from the group consisting of fluoro elastomer, elastic plastic, silicon, fluorine, and combinations thereof. 
         [0015]    In one embodiment, the non-coating portion includes a first non-coating portion at an outermost layer of the electrode assembly and a second non-coating portion at an edge of the electrode assembly in the first direction, and the flexible current collector is attached to the first non-coating portion or the second non-coating portion. The non-coating portion of the electrode assembly may be electrically insulated from the can. 
         [0016]    According to another embodiment of the present invention, a secondary battery includes: a can including an inner space; an electrode assembly including a coating portion and a non-coating portion and inserted in the can; at least one wire including an end connected to the non-coating portion; an electrode terminal connected to the other end of the wire; an insulation member disposed at an upper part of the electrode terminal; and a cap plate disposed at an upper part of the insulation member, wherein the electrode terminal penetrates the cap plate. 
         [0017]    The wire may be coupled to the non-coating portion by ultrasonic welding. The wire may be coated. The wire may include a plurality of strings. The wire may include a plurality of stings that are twisted. The insulation member may be disposed between the electrode terminal and the cap plate. 
         [0018]    According to another aspect of embodiments of the present invention, the non-coating portions of the electrode assembly are connected to the electrode terminals by using wires so that flexibility can be increased in the selection of components while reducing manufacturing costs and increasing production efficiency. 
         [0019]    According to an aspect of another embodiment of the present invention in which wires are used each having a plurality of strings, the wires can be more flexibly adjusted according to movement of the electrode assembly. 
         [0020]    According to an aspect of another embodiment of the present invention, the durability of the wires can be improved by twisting the plurality of strings of the wires. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The above and other features and advantages will become more apparent to those of ordinary skill in the art by describing in detail some exemplary embodiments of the present invention with reference to the attached drawings. Moreover, additional aspects and/or advantages of embodiments of the present invention are set forth in the following description and accompanying drawings, or may be obvious in view thereof to those skilled in the art. 
           [0022]      FIG. 1  is a perspective view of a secondary battery according to an embodiment of the present invention; 
           [0023]      FIG. 2  is a sectional view of the secondary battery of  FIG. 1 , taken along the line A-A; 
           [0024]      FIG. 3  is an exploded perspective view of the secondary battery of  FIG. 1 ; 
           [0025]      FIG. 4  is a sectional view of a secondary battery according to another embodiment of the present invention; 
           [0026]      FIG. 5  is a sectional view of a secondary battery according to another embodiment of the present invention; and 
           [0027]      FIG. 6  is an exploded perspective view of a secondary battery according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Some exemplary embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings. However, embodiments of the present invention may be embodied in different forms and should not be construed as limited to the exemplary embodiments illustrated and set forth herein. Rather, these exemplary embodiments are provided by way of example for understanding of the invention and to convey the scope of the invention to those skilled in the art. 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. As such, the drawings and description are to be regarded as illustrative in nature and not restrictive. 
         [0029]    A structure of a secondary battery according to an exemplary embodiment of the present invention will be described below. 
         [0030]      FIG. 1  is a perspective view illustrating a secondary battery  100  according to an exemplary embodiment of the present invention.  FIG. 2  is a sectional view illustrating the secondary battery  100 .  FIG. 3  is an exploded perspective view illustrating the secondary battery  100 . 
         [0031]    Referring to  FIGS. 1 through 3 , the secondary battery  100  according to one embodiment includes a can  110 , an electrode assembly  120 , flexible current collectors  140 , electrode terminals  150  and  151 , first insulation members  160 , a cap plate  170 , and second insulation members  180 . Nuts  190  may be tightened on the electrode terminals  150  and  151  disposed on the outer side of the cap plate  170 . 
         [0032]    The can  110  may have a shape such as a hexahedron shape. The can  110  includes a space to receive the electrode assembly  120 . In one embodiment, the can  110  is formed of a conductive metal material, such as aluminum, aluminum alloy, and/or steel plated with nickel. 
         [0033]    The electrode assembly  120  is disposed in the can  110 . The electrode assembly  120  includes a separator (not shown) disposed between positive and negative electrode plates. The electrode assembly  120 , in one embodiment, is a jelly roll-type electrode assembly in which the positive electrode plate, the separator, and the negative electrode plate are wound about an axis, such as in a spiral or vortex shape. The electrode assembly  120 , in one embodiment, includes a coating portion  121  coated with an active material, and non-coating portions  122  where the electrode plates are exposed and the active material is not coated. The non-coating portions  122 , in one embodiment, protrude from both sides of the coating portion  121  and are connected to the flexible current collectors  140 . 
         [0034]    The flexible current collectors  140 , in one embodiment, are coupled to the respective non-coating portions  122  of the electrode assembly  120 . That is, in one embodiment, the flexible current collectors  140  are provided in a pair and are connected to the positive and negative electrode plates of the electrode assembly  120 , respectively. In one embodiment, the flexible current collectors  140  may be wires, but embodiments of the present invention are not limited thereto. 
         [0035]    In one embodiment, ends of the current collectors  140  are respectively connected to the electrode plates by coupling of the current collectors  140  to the non-coating portions  122 . The current collectors  140 , in one embodiment, are coupled to the non-coating portions  122  by ultrasonic welding but, alternatively, may be coupled by any other suitable device or method. Further, in one embodiment, the other ends of the current collectors  140  are respectively connected (e.g., by ultrasonic welding) to the electrode terminals  150  and  151  so that the non-coating portions  122  are electrically connected to the respective electrode terminals  150  and  151 . 
         [0036]    The current collectors  140  are flexible such that the coupling between the non-coating portions  122  and the current collectors  140  can be maintained even when an impact is applied to the secondary battery  100 . In one embodiment, for example, the current collectors  140  may be formed of aluminum (Al) or copper (Cu) but, alternatively, may be formed of any other suitable material or combination of materials. 
         [0037]    Because the current collectors  140  are flexible, the positions of the electrode assembly  120  and the electrode terminals  150  and  151  are not rigidly determined. Also, since the electrode terminals  150  and  151  can be disposed at desired positions, inner components of the secondary battery  100  can be flexibly selected. Therefore, the number and/or cost of components of the secondary battery  100  can be decreased. 
         [0038]    In addition, since the current collectors  140  occupy less space than conventional collectors, space within the can  110  can be efficiently used, for example, to reduce the weight of the secondary battery  100 . In one embodiment, the current collectors  140  may be coated, such as with a material selected from the group consisting of fluoro elastomer, elastic plastic, silicon, fluorine, and combinations thereof, for insulation purposes, so as not to react with an electrolyte contained in the can  110 , for example. 
         [0039]    The electrode terminals  150  and  151  are electrically connected to the electrode assembly  120  through the current collectors  140 . The electrode terminals  150  and  151 , in one embodiment, are fixed to the cap plate  170  by using the first insulation members  160  so that the electrode terminals  150  and  151  can be electrically insulated from the cap plate  170 . The electrode terminal  150  connected to one of the current collectors  140  has a first polarity, and the electrode terminal  151  connected to the other of the current collectors  140  has a second polarity. The electrode terminals  150  and  151 , in one embodiment, protrude outward from the cap plate  170 . 
         [0040]    The first insulation members  160 , in one embodiment, are coupled to upper parts of the electrode terminals  150  and  151 . Lower sides of the first insulation members  160  may be supported by the electrode terminals  150  and  151  and may be fixed by tightening the nuts  190  on the electrode terminals  150  and  151 . 
         [0041]    Due to the first insulation members  160 , the electrode terminals  150  and  151  and the current collectors  140 , in one embodiment, do not make contact with the can  110  so that the can  110  can be electrically independent from the electrode terminals  150  and  151  and the current collectors  140 . Further, in one embodiment, the first insulation members  160  fix the electrode assembly  120  in the can  110  so that the electrode assembly  120  does not move in the can  110 . 
         [0042]    The first insulation members  160  may include gaskets  160   a  to prevent or substantially prevent leakage of electrolyte between the cap plate  170  and the first insulation members  160 . The gaskets  160   a  fill gaps between the first insulation members  160  and the cap plate  170  to prevent or substantially prevent leakage of the electrolyte. 
         [0043]    The cap plate  170  is coupled to an upper part of the can  110  and seals the can  110 . The cap plate  170 , in one embodiment, is welded along the edge of the can  110 . After electrolyte is filled in the can  110 , an injection hole of the cap plate  170  may be closed by using an injection hole plug  171 . In addition, the cap plate  170  may include a safety vent  172  which is thinner than other regions of the cap plate  170  so that the safety vent  172  can be first opened if the internal pressure in the can  110  reaches or exceeds a predetermined value. 
         [0044]    The electrode terminals  150  and  151 , in one embodiment, penetrate the cap plate  170  and protrude upward from the cap plate  170 . The electrode terminals  150  and  151 , in one embodiment, are electrically insulated from the cap plate  170  by the first insulation members  160  and the gaskets  160   a.    
         [0045]    The second insulation members  180  are coupled to the electrode terminals  150  and  151  from an upper side of the cap plate  170 . The second insulation members  180 , in one embodiment, are disposed around the electrode terminals  150  and  151  between the electrode terminals  150  and  151  and the cap plate  170 . In one embodiment, due to the second insulation members  180 , the electrode terminals  150  and  151  do not make contact with the cap plate  170  so that the electrode terminals  150  and  151  can be electrically insulated from the cap plate  170 . 
         [0046]    The nuts  190 , in one embodiment, are coupled to the electrode terminals  150  and  151  from the upper side of the second insulation members  180 . The nuts  190  are threadedly coupled to upper parts of the electrode terminals  150  and  151 . The electrode terminals  150  and  151  are physically coupled to the cap plate  170  by the nuts  190  so that the positions of the electrode terminals  150  and  151  can be fixed. 
         [0047]    As described above, in the secondary battery  100  according to one embodiment, the non-coating portions  122  of the electrode assembly  120  are connected to the electrode terminals  150  and  151  through the current collectors  140  so that the non-coating portions  122  of the electrode assembly  120  are not detached even when an impact is applied. 
         [0048]    In addition, because the current collectors  140  have smaller volumes than conventional collectors, the inside space of the can  110  can be efficiently used, and the electrode terminals  150  and  151  can be flexibly designed. In addition, due to the current collectors  140 , the weight of the secondary battery  100  can be reduced, and the number and cost of components of the secondary battery  100  can be reduced. 
         [0049]    A secondary battery according to another embodiment of the present invention will now be described below. 
         [0050]      FIG. 4  is a sectional view illustrating a secondary battery  200  according to another embodiment of the present invention. Elements having the same structures and functions as those of the corresponding elements of the previously described embodiment are denoted by the same reference numerals, and only the differences will be described. 
         [0051]    Referring to  FIG. 4 , the secondary battery  200  according to one embodiment includes the can  110 , the electrode assembly  120 , current collectors  240 , the electrode terminals  150  and  151 , the first insulation members  160 , the cap plate  170 , the second insulation members  180 , and the nuts  190 . 
         [0052]    In the secondary battery  200 , each of the current collectors  240  includes a plurality of wires, or strings. Since each of the current collectors  240  is constituted by a plurality of separate wires, the current collectors  240  can be flexibly adjusted according to a movement of the electrode assembly  120 . 
         [0053]    In addition, since the current collectors  240  may experience a lesser stress from a movement of the electrode assembly  120  as compared with a stress exerted on a single wire, the connection between the electrode assembly  120  and the electrode terminals  150  and  151  using the current collectors  240  can be more reliably maintained. That is, the coupling reliability of the current collectors  240  is high. 
         [0054]    A secondary battery according to another embodiment of the present invention will now be described below. 
         [0055]      FIG. 5  is a sectional view illustrating a secondary battery  300  according to another embodiment of the present invention. 
         [0056]    Referring to  FIG. 5 , the secondary battery  300  according to one embodiment includes the can  110 , the electrode assembly  120 , current collectors  340 , the electrode terminals  150  and  151 , the first insulation members  160 , the cap plate  170 , the second insulation members  180 , and the nuts  190 . 
         [0057]    In the secondary battery  300 , each of the current collectors  340  includes a plurality of wire, or strings. The plurality of wires of the current collectors  340  are twisted. Therefore, the current collectors  340  can be flexibly adjusted when the electrode assembly  120  is moved, and in addition, the durability of the current collectors  340  can be improved. 
         [0058]    Therefore, fatigue failure of the current collectors  340  caused by movement of the electrode assembly  120  can be reduced, and the connection between the electrode assembly  120  and the electrode terminals  150  and  151  can be reliably maintained. 
         [0059]    A secondary battery according to another embodiment of the present invention will now be described below. 
         [0060]      FIG. 6  is an exploded perspective view illustrating a secondary battery  400  according to another embodiment. 
         [0061]    Referring to  FIG. 6 , the secondary battery  400  according to one embodiment includes the can  110 , a plurality of electrode assemblies  420 , current collectors  440 , the electrode terminals  150  and  151 , the first insulation members  160 , the cap plate  170 , the second insulation members  180 , and the nuts  190 . 
         [0062]    The secondary battery includes a plurality of electrode assemblies  420  in the can  110 . The number of the electrode assemblies  420  is at least two. The electrode assemblies  420  are inserted in the can  110 . In one embodiment, each of the electrode assemblies  420  includes a coating portion  421  and non-coating portions  422 . In  FIG. 6 , the electrode assemblies  420  are shown being horizontally arranged side by side. However, in another embodiment, the electrode assemblies  420  may be vertically stacked. 
         [0063]    The current collectors  440 , in one embodiment, are coupled to the non-coating portions  422  of the electrode assemblies  420 . The current collectors  440  are respectively connected to the electrode terminals  150  and  151  so that the electrode assemblies  420  can be electrically connected to the electrode terminals  150  and  151 . 
         [0064]    The non-coating portions  422  of the electrode assemblies  420  may be connected to the electrode terminals  150  and  151  through the current collectors  440  according to polarities so that the electrode assemblies  420  can be connected in parallel to each other. Alternatively, the non-coating portions  422  of the electrode assemblies  420  may be connected in series to each other by the current collectors  440 , and then the current collectors  440  may be connected to the electrode terminals  150  and  151  (this configuration is not shown). 
         [0065]    Since the current collectors  440  occupy less space in the can  110  than conventional collectors, the plurality of electrode assemblies  420  can be disposed in the can  110 . That is, due to the current collectors  440 , the secondary battery  400  can include more electrode assemblies  420  to increase capacity. 
         [0066]    Some exemplary embodiments of a secondary battery have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purposes of limitation. It will be understood by those of ordinary skill in the art that various changes in form and details may be made to the embodiments described herein without departing from the spirit and scope of the present disclosure as set forth in the following claims.