Abstract:
A rechargeable battery comprises an electrode assembly comprising a plurality of electrodes, wherein each of the plurality of electrodes comprises a coated region and an uncoated region; a case housing the electrode assembly; a cap plate coupled to the case for enclosing the electrode assembly in the case; a current collection plate coupled to the cap plate; and a connecting member electrically connected to the uncoated regions of at least two electrodes.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/428,566, filed on Dec. 30, 2010, with the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     The described technology relates generally to a rechargeable battery having an electrode assembly and a current collecting plate connected to each other through a welding structure. 
     2. Description of the Related Technology 
     A rechargeable battery typically includes an electrode assembly, a case for housing the electrode assembly, a cap plate for opening and closing an opening of the case, a current collecting plate connected to an uncoated region of the electrode assembly, and an electrode terminal electrically connected to the current collecting plate and protruded to the outside of the cap plate. The electrode assembly typically includes a separator and positive and negative electrodes disposed on both sides of the separator, which are spirally wounded in a jelly-roll shape. 
     The uncoated region and the current collecting plate are typically mechanically and electrically connected to each other through welding. For example, an uncoated region is typically laid over a current collecting plate, and the uncoated region is typically welded to the current collecting plate by applying ultrasonic wave vibration in an ultrasonic welding method. If a width of the uncoated region is narrow, it is difficult to join the uncoated regions between a horn and an anvil of an ultrasonic welder. 
     In a laser welding method, a protrusion member of a current collecting plate is typically stood vertically on the uncoated region, and the protrusion member is typically welded to the uncoated region by radiating a laser beam. However, it is difficult to ensure that the uncoated region is uniformly adhered to the current collecting plate. 
     In laser welding, a slit is formed at the current collecting plate, and the uncoated region is inserted into the slit. Even in this case, it is also difficult to join the uncoated regions when a width of the uncoated region is narrow, and the separator may be damaged because the laser beam penetrates through the electrode assembly after passing through the uncoated region. 
     In order to improve welding performance, a contact area of the current collecting plate and the uncoated region can be widened by bending a predetermined part of the uncoated region. In this case, it is difficult to bend the uncoated region with a constant width. Further, it is difficult to spirally wind the bended positive electrode or the bended negative electrode. 
     The information disclosed in this section is only for enhancement of understanding of the background of the described technology and therefore may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     One embodiment provides a rechargeable battery including an electrode assembly comprising a plurality of electrodes, wherein each of the plurality of electrodes comprises a coated region and an uncoated region; a case housing the electrode assembly; a cap plate coupled to the case for enclosing the electrode assembly in the case; a current collection plate coupled to the cap plate; and a connecting member electrically connected to the uncoated regions of at least two electrodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rechargeable battery according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of  FIG. 1  taken along the line II-II. 
         FIG. 3  is an exploded perspective view illustrating an electrode assembly and a current collecting plate. 
         FIG. 4  is a cross-sectional view of  FIG. 3  taken along the line IV-IV. 
         FIG. 5  is a cross-sectional view of an electrode assembly and a current collecting plate of a rechargeable battery according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
       FIG. 1  is a perspective view of a rechargeable battery according to a first embodiment of the present invention.  FIG. 2  is a cross-sectional view of  FIG. 1  taken along the line II-II. Referring to  FIG. 1  and  FIG. 2 , a rechargeable battery  100  may include a case  20  for housing an electrode assembly  10 , a cap plate  30  connected to an opening formed at one side of the case  20  for closing and opening the case  20 , current collecting plates  41  and  42  electrically connected to the electrode assembly  10 , and electrode terminals  51  and  52  connected to the current collecting plates  41  and  42  and penetrating the cap plate  30 . 
     For example, the electrode assembly  10  may include a separator  13  as an insulator and negative and positive electrodes  11  and  12  disposed at both sides of the separator  13 . The electrode assembly  10  may have a jelly roll shape formed by spirally winding the negative electrode  11  and the positive electrode  12  with the separator  13 . Further, the electrode assembly may be formed by stacking the negative electrode and the positive electrode with the separator interleaved therebetween although it is not shown. Here, the negative and positive electrodes are a single metal plate. Further, the electrode assembly may be formed by folding the negative electrode, the separator, and the positive electrode in a zigzag manner (not shown). 
     The negative electrode  11  and the positive electrode  12  may be formed by coating a current collector with an active material. Here, the current collector may be a thin metal plate. Therefore, the negative electrode  11  and the positive electrode  12  may be divided into a coating region where the current collector is coated with the active material, and uncoated regions  111  and  121  where the current collector is not coated with the active material. The coating region may occupy almost the entire area of the negative electrode  11  and the positive electrode  12 . The uncoated regions  111  and  121  may be formed at both sides of the coating region of the electrode assembly  10  in the jelly-roll state. For example, the current collector of the negative electrode  11  may be made of copper, and the current collector of the positive electrode  12  may be made of aluminum. 
     The case  20  forms an exterior of the rechargeable battery  100 . The case  20  may be made of conductive metal such as aluminum, aluminum alloy, or nickel-plated steel. The case  20  can provide a space for housing the electrode assembly  10 . For example, the case  20  may be formed in a cuboid shape including an opening at one end thereof for housing the electrode assembly  10  that also has a cuboid shape. As shown in  FIG. 1  and  FIG. 2 , the opening faces upwardly (z-axis direction) 
     The cap plate  30  may be formed of a thin plate and connected to the opening. Accordingly, the cap plate  30  can close and seal the case  20 . Such a cap plate  30  may include elements for forming and driving the rechargeable battery  100  by blocking an inside and an outside of the case  20  from each other or connecting the inside and the outside according to needs. For example, the cap plate  30  may include terminal holes  311  and  312  penetrating the electrode terminals  51  and  52 , an electrolyte injection opening  32  for injecting the electrolyte solution, and a vent hole  35  for securing the stability of the rechargeable battery  100 . 
     The electrolyte injection opening  32  may be sealed with a sealing cap  33  after injecting the electrolyte solution inside the case with the cap plate  30  connected to the case  20 . The vent hole  35  may be sealed with a vent plate  34  that maintains a closing state and opens the vent hole  35  when an internal pressure increases. 
     The electrode terminals  51  and  52  penetrating the terminal holes  311  and  321  are installed at the terminal holes  311  and  312 . The electrode terminals  51  and  52  are electrically connected to the negative electrode  11  and the positive electrode  12  of the electrode assembly  10 . The electrode terminals  51  and  52  may be installed with the insulators  511  and  521  interposed at inner sides of the terminal holes  311  and  312  and with gaskets  512  and  522  interposed at outer sides of the terminal holes  311  and  312 . liquid injection device having an injection portion arranged to inject the molten metal at a corresponding location welded to the current collection plate  41  may be used. In the entire length L of the uncoated region  111 , the connecting member  70  may be formed within a connecting member length L 1  that does not intrude the coating regions  112  and  122 , the separator  13 , and the positive electrode  12 . Therefore, the connecting member length L 1  can widen a welding area of the current collecting plate  41 , protect the coating regions  112  and  122  and the separator  13  from damage, and prevent the negative electrode  11  and the positive electrode  12  from short-circuit. 
     Since the connecting member  70  widens a contact area of the uncoated region  111  and the current collecting plate  41 , the welding performance may be improved when the connecting member  70  of the electrode assembly  10  is welded to the current collecting plate  41  using a laser beam, 
     Although the uncoated region  111  has low welding performance because it is made of copper, the connecting member  70  formed at the uncoated region  111  can improve the welding performance of the uncoated region  111  and the current collecting plate  41 . 
     For example, the connecting member  70  may be formed with insert copper injected and then hardened between the space C of the uncoated region  111  and at the end of the uncoated region  111 . That is, the connecting member  70  can include copper  71  in the molten state additionally provided and copper  72  in the molten state at the end of the uncoated region  111  melted by the molten copper  71 . That is, the connecting member  70  may be integrally formed at the connecting member range L 1  by the copper  71  and  72  that are made of the same material and molten and then hardened. 
     The connecting member  70  may be formed in a width direction (y-axis direction) at a predetermined gap setup for a height direction (z-axis direction) of the uncoated region  111 . The current collecting plate  41  can closely adhere to and be welded to the uncoated region  111  corresponding to the connecting member  70 . That is, the connecting member  70  can minimize the possibility of damaging the electrode assembly  10 , which may be caused by the molten and then hardened copper  71  and  72  formed at a predetermined area including an area where the current collecting plate  41  is welded. The current collecting plate  41  may include a welding unit  411  corresponding to the connecting member  70  and a through-hole  412  not corresponding to the connecting member  70 . Accordingly, the current 
     The insulators  511  and  521  may electrically insulate the electrode terminals  51  and  52  and the cap plate  30 . Further, the insulators  511  and  521  may further extend at the inside of the cap plate  30  between the current collecting plates  41  and  42  and the cap plate  30 , thereby electrically insulating the current collecting plates  41  and  42  and the cap plate  30 . The gaskets  512  and  522  may form a sealing structure between the electrode terminals  51  and  52  and the terminal holes  311  and  312  by assembling the electrode terminals  51  and  51  with nuts  61  and  62 . 
     The current collecting plates  41  and  42  may electrically connect the electrode assembly  10  and the electrode terminals  51  and  52 . For example, the current collecting plates  41  and  42  may be electrically connected to the electrode terminals  51  and  52  by caulking or riveting the electrode terminals  51  and  52  installed at the terminal holes  311  and  312  from the inside of the cap plate  30 . Further, the current collecting plates  41  and  42  may be connected to the uncoated regions  111  and  121  of the electrode assembly  10  through welding. 
     Since the connection structures of the uncoated regions  111  and  121  of the electrode assembly  10  and the current collecting plates  41  and  42  are identically formed at the negative electrode  11  and the positive electrode  12 , the connection structure of the uncoated region  111  and the current collection plate  41  of the negative electrode  11  will be used as an example to describe the present invention, hereinafter. 
       FIG. 3  is an exploded perspective view illustrating an electrode assembly and a current collecting plate.  FIG. 4  is a cross-sectional view of  FIG. 3  taken along the line IV-IV. Referring to  FIG. 3  and  FIG. 4 , an empty space C may be formed between uncoated regions  111  in a spiral-wound electrode assembly  10 . The electrode assembly  10  may include a connecting or reinforcing member  70  formed by interposing an insert metal that is formed by injecting and then hardening molten metal at the space C between the uncoated regions  111 . 
     The inserted metal may form the connecting member  70  by partially injecting molten metal at a location corresponding to the uncoated region  111  to which the current collection plate  41  is to be connected and then hardening the molten metal. Further, the insert metal may form the connecting member  70  by partially soaking the uncoated region  111  in the molten metal and then hardening the molten metal. For this, a molten metal collecting plate  41  may minimize deformation caused by heat generated from welding and discharge a gas generated inside the electrode assembly during charging and discharging. That is, the through-hole  412  may be disposed alternately with the welding unit  411 . 
     The connecting member may be formed corresponding to an entire area of a side of the uncoated region  111 , which is setup as a height-width direction. In this case, the increment of an area of the connecting member in the uncoated region may make it further easier to weld the current collecting plate with the connecting member (not shown). 
     Also, the connecting member  70  may be formed by filling the space C between the uncoated regions  111  with the molten and then hardened copper  71 . Accordingly, it may prevent a laser beam from penetrating the inside of the electrode assembly  10  during welding. That is, the connecting member  70  may protect the coating regions  112  and  122  and the separator  13  from damage caused by the laser beam. 
       FIG. 5  is a cross-sectional view of an electrode assembly  210  and a current collecting plate  241  in a rechargeable battery according to a second embodiment of the present invention. 
     The connecting member  70  may be formed using molten copper having a melting point identical to that of the uncoated region  111  in the first described embodiment. Unlike the first embodiment, a connecting or reinforcing member  270  may be formed using insert aluminum having a melting point lower than that of an uncoated region  211  and molten and then hardened in the second described embodiment. 
     In the first described embodiment, the connecting member  70  is integrally formed at the end of the uncoated region  111  by the copper  71  and  72  molten and then hardened. Unlike the first embodiment, the connecting member  270  may be formed as a layered structure of copper formed at an end member  272  of the uncoated region  211  and the insert aluminum  271  interposed between the end members  272  of the uncoated region  211 . 
     Since the insert aluminum  271  has a melting point lower than that of the copper, the connecting member  270  of the second described embodiment may reduce the possibility of damaging the uncoated region  211  more than the connecting member  70  of the first described embodiment. That is, the end member  272  sustains a shape thereof in the connecting member  270 . 
     In detail, the connecting member  270  may form a connecting member length L 1  that does not intrude the coating regions  112  and  122 , the separator  13 , and the positive electrode  12  in the entire length L of the uncoated region  211 . Accordingly, the connecting member length L 1  can widen a welding area of the current collecting plate  241 , protect the coating regions  112  and  122 , the separator  13 , and the positive electrode  12  from damage caused by melting metal, and prevent the negative electrode  11  and the positive electrode  12  from short-circuit. 
     Since the connecting member  270  enlarges the contact area of the uncoated region  211  and the current collecting plate, welding performance is further improved when the connecting member  270  of the electrode assembly  210  is welded to the current collecting plate  241  using a laser beam. Although the uncoated region  211  has a low welding property because it is made of copper, the connecting member  270  formed at the uncoated region  211  can improve the welding performance of the uncoated region  211  and the current collecting plate  241 . 
     For example, the connecting member  270  may include the end member  272  of the uncoated region  211  and insert aluminum  271  filling the space C of the uncoated region  211 . That is, the connecting member  270  may be formed as a stacked structure of the insert aluminum  271  and the copper end member  272 . That is, the connecting member  270  may be formed as a layered structure of the insert aluminum  271  and the copper end member  272  in the connecting member range L 1 . 
     Further, the connecting member  270  can prevent a laser beam from penetrating the inside the electrode assembly by filling the space C between the uncoated regions  211  with the insert aluminum  271 . That is, the connecting member  270  can prevent the separator  13  from damaging which is caused by the laser beam. 
     While this invention has been described in connection with what is presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.