Abstract:
A rechargeable battery having a current collector plates that a have a stable and reliable connection to an uncoated portion of one of the anode and the cathode of the electrode assembly. The rechargeable battery includes the electrode assembly, a case, a cap assembly, and the current collecting plates. The electrode assembly includes the anode, the cathode, and a separator arranged between the anode and the cathode. The case houses the electrode assembly. The cap assembly closes and seals the case and includes an electrode terminal. The current collecting plates connect the electrode assembly and the cap assembly and each include a plurality of current collecting protrusions that extend into the electrode assembly. The current collecting protrusions of one current collector plate are arranged among the current collecting protrusions of another current collecting plate, and the uncoated region of one of the anode and the cathode is arranged among these current collecting protrusions.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from an application earlier filed in the Korean Intellectual Property Office on 27 Sep. 2007 and there duly assigned Serial No. 10-2007-0097307. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a rechargeable battery having an improved structure of a current collecting plate electrically connected to an electrode assembly. 
         [0004]    2. Description of the Related Art 
         [0005]    Rechargeable batteries can be repeatedly charged and discharged, unlike a primary battery that is incapable of being recharged. A low capacity rechargeable battery composed of a single cell is generally used for a portable small electronic device, such as a mobile phone, a laptop computer, and a camcorder. A large capacity rechargeable battery composed of a plurality of cells connected in a form of a pack is widely used to drive a motor for a hybrid electric vehicle. Such rechargeable batteries are serially connected to form a rechargeable battery module to drive a motor for an electric vehicle, which needs a large amount of electric power. 
         [0006]    Such a rechargeable battery is manufactured in various forms. The representative form of a rechargeable battery is a cylindrical form or a quadrilateral form. The rechargeable battery includes an electrode assembly having an anode and a cathode with a separator interposed therebetween, a case for providing a space for housing the electrode assembly, and a cap assembly for closing and sealing the case. 
         [0007]    In the case of a rechargeable battery formed in a cylindrical shape, an uncoated region, where an active material is not coated, are formed in the anode and the cathode of the electrode assembly, and a positive uncoated region and a negative uncoated region are disposed to face in different directions. 
         [0008]    A cathode current collecting plate is adhered on the negative uncoated region and an anode current collecting plate is adhered on the positive uncoated region. The cathode current collecting plate is electrically connected to the case, and the anode current collecting plate is electrically connected to the cap assembly to allow current to pass to the outside. Therefore, the case is operated as a negative terminal, and the cap plate mounted in the cap assembly is operated as a positive terminal. 
         [0009]    Since the anode current collecting plate and the cap assembly are electrically connected by a lead member made of a conductive metal, the lead member, the anode current collecting plate, and the cap assembly are welded together and then inserted into the case. After the cap assembly is inserted, the cap assembly is fixed to the case by clamping the cap assembly. 
         [0010]    Since current is drawn out to the outside through the current collecting plate that is electrically connected to the electrode assembly, it is very important to have a stable connection between current collecting plate and the electrode assembly. 
         [0011]    In the case of a high power battery, high current flows through the current collecting plate. Therefore, the smaller the resistivity of the current collecting plate, the more current loss can be reduced. Accordingly, it is preferable to form the current collecting plate to have a large thickness. However, if the thickness of the current collecting plate is too thick, heat is not fully transferred to the electrode assembly and so it is difficult to weld the current collecting plate to the electrode assembly. 
         [0012]    Conventionally, the current collecting plate and the electrode assembly are simply welded together at a surface contact of the current collecting plate and the electrode assembly. Since no structure supports the current collecting plate in a side direction, the contact between the electrode assembly and the current collecting plate becomes poor weak an external impact is applied. If the contact between the current collecting plate and the electrode assembly becomes poor, the resistivity around the contact increases. Therefore, the output of the rechargeable battery becomes reduced and the rechargeable battery generates a large amount of heat. What is therefore needed is an improved design for a rechargeable batter where the contact between the electrode assembly and the current collecting plate that is strong and reliable enough to withstand various forms of impact. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention has been made in an effort to provide a rechargeable battery having the advantage of having a current collecting plate that has a strong, stable and reliable electrical connection to an electrode assembly. 
         [0014]    It is a technical subject of the present invention to provide a rechargeable battery having a current collecting plate that has a stable and reliable connection to an electrode assembly. 
         [0015]    It is another technical subject of the present invention to provide a rechargeable battery for providing an enhanced output by reducing the resistivity of a current collecting plate. 
         [0016]    An exemplary embodiment of the present invention provides a rechargeable battery. The rechargeable battery includes an electrode assembly, a case, a cap assembly, and a current collecting plate, the electrode assembly includes an anode, a cathode, and a separator arranged between the anode and the cathode, the anode, the cathode and the separator arranged as a plurality of windings, each of the anode and the cathode having a coated region and an uncoated region, a case adapted to house the electrode assembly, a cap assembly including an electrode terminal, the cap assembly adapted to close and seal the case and a plurality of current collecting plates adapted to electrically connect the electrode assembly to the cap assembly, each of the plurality of current collecting plates includes a plurality of current collecting protrusions extending into the electrode assembly, wherein the plurality of current collecting protrusions of one of the plurality of current collecting plates are arranged among a plurality of current collecting protrusions of another of said plurality of current collecting plates, and wherein ones of the plurality of windings of the uncoated region of one of the anode and the cathode are arranged among the plurality of current collecting protrusions of the one and the another of the plurality of current collecting plates. 
         [0017]    Each of the plurality of current collecting plates can further include a flat part, each of the plurality of current collecting protrusions can protrude from the flat part. Each of the plurality of current collecting protrusions can include an inclined protrusion part that adapted to protrude from and the flat part and an incline and from the flat part and towards the electrode assembly, an extended protrusion part adapted to protrude from the inclined protrusion part, the extended protrusion part being in parallel with the flat part and an inserting protrusion part that adapted to protrude from the extended protrusion part and towards one of said plurality of windings of the uncoated region of one of the anode and the cathode. The inserting protrusion part can have one end arranged as a wedge shape. Adjacent ones of the plurality of current collecting protrusions can be arranged to have the extended protrusion parts located in a same plane. Each of the plurality of current collecting plates can be fixed to ones of the plurality of windings of the uncoated region of one of the anode and the cathode via a weld, ones of the plurality of windings of the uncoated region of the one of the anode and the cathode can be arranged among ones of the plurality of current collecting protrusions of both the one and the another of the plurality of current collecting plates. Ones of the plurality of windings of the uncoated region of the one of the anode and the cathode can be fixed to the extended protrusion parts of ones of the plurality of current collecting protrusions of both the one and the another of the plurality of current collector plates via a weld. The plurality of current collecting plates can consist of only two current collecting plates. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
           [0019]      FIG. 1  is a cross-sectional perspective view of a rechargeable battery according to an exemplary embodiment of the present invention; 
           [0020]      FIG. 2  is a perspective view of a current collecting plate according to an exemplary embodiment of the present invention; 
           [0021]      FIG. 3  is a partial perspective view of an electrode assembly attached to a current collecting plate according to an exemplary embodiment of the present invention; 
           [0022]      FIG. 4  is a front view of the electrode assembly attached to the current collecting plate of,  FIG. 3 ; and 
           [0023]      FIG. 5  is a side view of the electrode assembly attached to the current collecting plate of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]      FIG. 1  is a cross-sectional perspective view of a rechargeable battery according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , the rechargeable battery  100  according to the present invention includes an electrode assembly  110  having an anode  112  and a cathode  113  with a separator  114  interposed between the anode  112  and the cathode  113 , and a case  120  having an opening formed at the top end to house the electrode assembly  110  and an electrolyte solution. A cap assembly  140  is disposed at the opening of the case  120  by using a gasket  144 . 
         [0025]    The case  120  is made out of a conductive metal such as steel coated with aluminum, an aluminum alloy, or nickel. The case  120 , according to the present exemplary embodiment, is formed in a cylindrical shape and has an internal space to house the electrode assembly  110 . After inserting the cap assembly  140  into the case  120 , the cap assembly  140  is fixed to the case  120  through clamping. In the clamping process, a beading part  123  and a clamping part  125  are formed. 
         [0026]    The electrode assembly  100 , according to the present exemplary embodiment, is formed in a cylindrical shape. That is, the anode  112 , the separator  114 , and the cathode  113  are sequentially wound into a plurality of windings to form the electrode assembly  110  in a cylindrical shape. However, the structure of the electrode assembly  110  is not limited thereto, and can be formed in other various structures. A space is formed in the center of the electrode assembly  110 , and a center pin  170  is disposed in the space for enabling the electrode assembly  110  to sustain the cylindrical shape. 
         [0027]    Referring to  FIG. 1 , a positive uncoated region  112   a  is formed at an upper end of the anode  112 . This uncoated region  112   a  is not coated with a positive active material. The anode  112  is electrically connected to an anode current collecting plate  160  at the positive uncoated region  112   a . Referring to  FIG. 1 , a negative uncoated region  113   a  is formed at the lower end of the cathode  113 . This negative uncoated region  113   a  is not coated with a negative active material. The cathode  113  is electrically connected to a cathode current collecting plate  132  at the negative uncoated region  113   a.    
         [0028]    The cap assembly  140  includes a cap plate  143  having a protruded outer terminal and an exhaust port  143   a , and a vent plate  142  disposed under the cap plate  143  for discharging gas by being broken when a predetermined pressure condition is satisfied. The vent plate  142  interrupts the electrical connection between the electrode assembly  110  and the cap plate  143  when the predetermined pressure condition occurs. 
         [0029]    Since a positive temperature coefficient element  141  is disposed between the cap plate  143  and the vent plate  142 , the positive temperature coefficient element  141  unlimitedly increases in electrical resistance when the temperature rises above a predetermined temperature. When the rechargeable battery  100  reaches a temperature higher than a predetermined value, the positive temperature coefficient element  141  interrupts the flow of current for charging and discharging. 
         [0030]    The vent plate  142  is protruded downwardly and includes a sub plate  147  attached at the bottom side of the protruded part. A middle plate  146  is disposed at the edge of the vent plate  142 , is fixed at the sub plate  147 , and electrically connects to the electrode assembly  110  through a lead unit  150 . An insulator  145  is disposed between the middle plate  146  and the vent plate  142  to insulate the middle plate  146  from the vent plate  142 . 
         [0031]    The anode current collecting plate  160  is made out of two current collecting plates  161  and  165  engaged together with each other. In the present exemplary embodiment, the anode current collecting plate is exemplary described. However, the present invention is not limited thereto, and the cathode current collecting plate can have the same structure as the anode current collecting plate according to the present exemplary embodiment. 
         [0032]    Referring to  FIG. 2 , the current collecting plate  161  will be described in detail. Since the two current collecting plates  161  and  165  facing each other have the same structure, only the current collecting plate  161  will be described and the description of the current collecting plate  165  will be omitted. 
         [0033]    The current collecting plate  161  includes a flat part  162  and a plurality of current collecting protrusions  163  protruded from the flat part  162 . The current collecting protrusions  163  are formed at one side of the flat part  162 . The current collecting protrusions  163  are protruded from the side of the flat part  162  in a front direction and are separated at a predetermined distance from each other. Each of the current collecting protrusions  163  includes an inclined protrusion part  163   a  protruded from the flat part  162  and inclined downwardly, an extended protrusion part  163   b  continuously formed from the inclined protrusion part  163   a  and protruded in parallel with the flat part  162 , and an inserting protrusion part  163   c  vertically continued from the extended protrusion part  163   b.    
         [0034]    The inserting protrusion part  163   c  has a pointed end allowing it to be easily inserted between the windings of positive uncoated region  112   a . The flat part  162  is formed in the shape of a flat semicircular board and includes a ventilation hole  164 . 
         [0035]    As shown in  FIG. 3 , the two current collecting plates  161  and  165  include flat parts  162  and  166  and a plurality of current collecting protrusions  163  and  167 . The flat parts  162  and  166  include ventilation holes  164  and  168 . The current collecting protrusions  163  and  167  protruded from the flat parts  162  and  166  are arranged to be crossed with each other, thereby making contact with the windings of the positive uncoated region  112   a.    
         [0036]      FIG. 3  exemplary illustrates the anode current collecting plate  160  disposed at the positive uncoated region  112   a . However, the present invention is not limited to the anode current collecting plate  160 , and the cathode current collecting plate can instead or also have the same structure. 
         [0037]    As shown in  FIGS. 4 and 5 , the current collecting plates  161  and  165  are disposed on the positive uncoated region  112   a , and the plurality of current collecting protrusions  163  and  167  extend into the windings of the positive uncoated region  112   a . The current collecting protrusions  163  and  167  are inserted mutually while the two current collecting plates  161  and  165  face each other. Accordingly, the extended protrusion parts  163   b  and  167   b  of the current collecting protrusions  163  and  167  are arranged in parallel in the same plane by being overlapped with each other. 
         [0038]    Referring to  FIG. 3 , a process of installing the current collecting plate  160  on the electrode assembly  110  will be described, hereinafter. At first, one current collecting plate  161  is disposed on the windings of the positive uncoated region  112   a . When the current collecting plate  161  is disposed on the windings of the positive uncoated region  112   a , current collecting protrusions  163  penetrate into the windings of the positive uncoated regions  112   a . Since the inserting protrusion part  163   c  of each current collecting protrusion  163  has one end formed in a wedge shape, the current collection protrusion  163  can easily penetrate into the windings of the positive uncoated region  112   a.    
         [0039]    After one current collecting plate  161  is placed on the windings of the positive uncoated region  112   a , another current collecting plate  165  is disposed on the windings of the positive uncoated region  112   a  to form a pair with the current collecting plate  161 . The current collecting protrusions  167  of the other current collecting plate  165  are disposed to cross the current collecting protrusions  163  of the previously disposed current collecting plate  161 . While the current collecting protrusions  167  of the current collecting plate  165  are penetrating into the windings of the positive uncoated region  112   a , the windings of the positive uncoated region  112   a  extend between the current collecting protrusions  163  and  167  and protruded. 
         [0040]    As the current collecting protrusions  163  and  167  are inserted between the windings of the positive uncoated region  112   a , the current collecting plate  160  is intertwined with the windings of the positive uncoated region  112   a . Therefore, the anode current collecting plate  160  is stably prevented from moving away from the electrode assembly  110 . 
         [0041]    The current collecting protrusions  163  and  167  are welded together with the windings of the positive uncoated region  112   a  that extends between the current collecting protrusions  163  and  167  to form a welding line  180  on the current collecting plate  160 . The current collecting plate  160  and the windings of the positive uncoated region  112   a  are disposed in the same plane as the welding line  180 . The welding is performed between the extensions  163   b  and  167   b  and the windings of the positive uncoated region  112   a  arranged in the same plane in parallel. 
         [0042]    If the windings of the positive uncoated region  112   a  and the anode current collecting plate  160  are disposed in the same plane, as in the present exemplary embodiment, the current collecting plate  160  can be stably welded to the windings of the positive uncoated region  112   a , even though the thickness of the current collecting plate  160  is made to be large. Conventionally, a laser is radiated to the current collecting plate, and the heat transferred from the current collecting plate is used to weld the windings of the uncoated region. Therefore, if the current collecting plate is made too thick, the heat is not properly transferred from the current collecting plate to the windings of the uncoated region. If the windings of the positive uncoated region  112   a  are protruded between the current collecting protrusions  163  and  167 , as in the present exemplary embodiment, the laser can be directly radiated onto the windings of the positive uncoated region  112   a  to melt the windings of the positive uncoated region  112   a . Therefore, the current collecting plate  160  can be stably welded even though the current collecting plate  160  is thick. 
         [0043]    Since the inserted current collecting protrusions  163  and  167  are welded with the windings of the positive uncoated region  112   a  as a medium, the current collecting protrusions  163  and  167  are integrally fixed at the windings of the positive uncoated region  112   a . Therefore, the current collecting plates  161  and  165  are prevented from being moved by an external impact. That is, since the members are not just simply inserted to each other, but are intertwined with each other like a spool of thread, the members are stably fixed together. 
         [0044]    While this invention has been described in connection with what is presently considered to be practical exemplary 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. 
         [0045]    As shown above, the current collecting plate is stably fixed at the uncoated regions by inserting the current collecting protrusions of the current collecting plate into the uncoated regions according to an embodiment of the present invention. Therefore, contact resistivity can be minimized according to an embodiment of the present invention. 
         [0046]    Since the current collecting plate and the windings of the uncoated region are welded in the same plane, the thickness of the current collecting plate can be made to be thick while providing for a strong, stable and reliable electrical connection between the current collecting plate and the electrode assembly. Therefore, the output of the rechargeable battery becomes improved because the resistivity of the current collecting plate is reduced.