Abstract:
A battery pack is disclosed. An embodiment of the battery pack includes a bare cell comprising a first surface, a positive electrode and a negative electrode; a circuit module disposed over the first surface and comprising a positive electrode terminal and a negative electrode terminal; a first lead plate disposed over the first surface and coupled to the positive electrode and the positive electrode terminal; and a second lead plate disposed over the first surface and coupled to the negative electrode and the negative electrode terminal; wherein the first surface of the bare cell is curved, and each lead plate has a curvature conforming to the first surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application No. 61/223,862, filed on Jul. 8, 2009, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments relate to a battery pack of a chargeable and dischargeable secondary battery. 
     2. Description of the Related Technology 
     In general, a battery pack of a chargeable and dischargeable secondary battery typically includes a bare cell having a case in which an electrode assembly is accommodated, and a protective circuit module (PCM) connecting the bare cell to an external terminal to control charge and discharge of the bare cell. 
     In the battery pack, a lamination-type electrode assembly, obtained by laminating a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate, is typically used as the electrode assembly of the bare cell. Otherwise, a wind-type electrode assembly is used as the electrode assembly of the bare cell, in which the electrode assembly is wound in a state such that the positive electrode plate, the negative electrode plate, and the separator interposed between the positive electrode plate and the negative electrode plate are laminated. The electrode assembly is typically accommodated in a cylindrical or polygonal can or a pouch type armoring material to form the bare cell. The bare cell is typically electrically connected to the PCM. 
     In existing battery packs, a supporting member is typically installed to electrically connect the bare cell to the PCM and to mechanically support the PCM installed in the bare cell. A supporting holder is installed as the supporting member. Molding resin is injected and filled in a gap formed between the bare cell and the protective circuit module in a hot melting to form the supporting member. The protective circuit module is supported by the molding resin. 
     When the supporting holder is used as the supporting member, fabrication cost increases because a separate structure is used. 
     When molding resin is injected in the hot melting as the supporting member, because of inferior formation of the molding resin, the protective circuit module can become inclined in the vertical direction or be twisted laterally. When the protective circuit module is vertically inclined, the external terminal of the protective circuit module is not properly connected to an external device. When the protective circuit module is twisted laterally, the external terminal of the protective circuit module deviates from an initial position so that assembly cannot be completed. 
     SUMMARY 
     An embodiment of the present invention includes a battery pack. 
     In accordance with an aspect of the present invention, a battery pack comprises a bare cell that comprises a first surface, a positive electrode and a negative electrode; a circuit module disposed over the first surface and comprising a positive electrode terminal and a negative electrode terminal; a first lead plate disposed over the first surface and coupled to the positive electrode and the positive electrode terminal; and a second lead plate disposed over the first surface and coupled to the negative electrode and the negative electrode terminal; wherein the first surface of the bare cell is curved, and each lead plate has a curvature conforming to the first surface. 
     In accordance with another aspect of the present invention, a battery pack comprises a bare cell comprising a first surface that has a curvature and a second and third surfaces that are coupled to the first surface; a circuit module disposed over the first surface of the bare cell; a first and second lead plate disposed over the first surface and coupled to the bare cell and the circuit module wherein at least a portion of the first and second lead plates adjacent the first surface are curved with substantially the same curvature as the first surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view illustrating a battery pack according to an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view illustrating a bare cell and a protective circuit board in the battery pack according to the embodiment of the present invention; 
         FIG. 3  is a view illustrating the bare cell coupled with the protective circuit board in the battery pack according to the embodiment of the present invention; 
         FIG. 4  is a front view of the battery pack of  FIG. 3 ; 
         FIG. 5  is a plan view of the battery pack of  FIG. 4 ; 
         FIG. 6  is a left side sectional view of the battery pack of  FIG. 4 ; and 
         FIG. 7  is a right side sectional view of the battery pack of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     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 . 
     The surfaces of the first and second lead plates  130  and  140 , which are seated on the bare cell  110 , may have the same shape as those of the surfaces that contact the bare cell  110 . 
     The battery pack  100  according to the embodiment of the present invention can further include an insulation member  160  disposed between the first lead plate  130  and the second lead plate  140  to insulate the same from each other, and can also include a label  170  fixing the bare cell  110  and the cover  150 . 
     The bare cell  110  may be obtained by accommodating an electrode assembly (not shown) in a can  111  made of a metal. The can  111  may be made of aluminum or an alloy of aluminum, but is not limited thereto. 
     The can  111  may be a polygonal can having an approximately rectangular parallelepiped. 
     The can  111  may include first and second rectangular surfaces  111   a  and  111   b  that are wide rectangular surfaces. Third, fourth, fifth, and sixth surfaces  111   c ,  111   d ,  111   e , and  111   f  integrated with the first and second surfaces  111   a  and  111   b  may be narrow rectangular surfaces. The third and fourth surfaces  111   c  and  111   d  may be short in length. The fifth and sixth surfaces  111   e  and  111   f  may be longer than the third and fourth surfaces  111   c  and  111   d.    
     The electrode assembly can include a positive electrode plate (not shown), a negative electrode plate (not shown), and a separator (not shown) interposed between the positive electrode plate and the negative electrode plate, which is the structure of a common electrode assembly. The positive electrode plate may be electrically connected to the can  111 , and the negative electrode plate may be electrically connected to an electrode terminal  112  that protrudes outside through the third surface  111   c  of the bare cell  110 . 
     The protective circuit module  120  can include a protective circuit board  121  and external terminals  122  mounted on one surface of the protective circuit board  121 . The protective circuit board  121  can include a protective circuit element  123  provided on the other surface to control the charge and discharge of the bare cell  110 . The protective circuit element  123  may make the charge state of the bare cell  110  uniform and prevent overcharge and overdischarge. The protective circuit board  121  can include a positive electrode connection terminal (not shown) and a negative electrode connection terminal (not shown) that are electrically connected to the positive electrode terminal and the negative electrode terminal of the bare cell  110 , respectively. 
     The first lead plate  130  electrically may connect the positive electrode terminal of the bare cell  110  to the positive electrode connection terminal of the protective circuit board  121 . The second lead plate  140  may electrically connect the negative electrode terminal of the bare cell  110  to the negative electrode connection terminal of the protective circuit board  121 . 
     The first and second lead plates  130  and  140  may be made of any electric conductive material. The first and second lead plates  130  and  140  may be made of nickel or a nickel alloy. However, embodiments of the present invention are not limited to the above. 
     The shape and structure of the first and second lead plates  130  and  140  are as follows. 
     The first lead plate  130  can include a board connection unit  131  formed on an end and connected to the positive electrode connection terminal of the protective circuit board  121 , a bare cell connection unit  132  formed on the other end and connected to the fourth surface  111   d  of the can  111  that corresponds to the positive electrode terminal of the bare cell  110 , and a connection unit  133  connecting the board connection unit  131  to the bare cell connection unit  132 . 
     The board connection unit  131  may be parallel with the protective circuit board  121  and may be electrically connected to the positive electrode connection terminal of the protective circuit board  121  by welding or the like. 
     The bare cell connection unit  132  may have a shape matching the shape of the fifth surface  111   e  of the bare cell  110  including the can  111 . The fifth surface  111   e  of the can  111  may have a rounded shape with a curvature. Therefore, the bare cell connection unit  132  can include a curvature piece  134  having the same or similar curvature as that of the curvature of the fifth surface  111   e  and a connector  135  bent from the curvature piece  134  at a right angle to be connected to the fourth surface  111   d  of the can  111 . The curvature piece  134  may have a larger width than that of the connector  135  so that the area that supports the protective circuit board  121  increases. The connector  135  may be connected to the fourth surface  111   d  of the can  111  through a first through hole  161  of the insulation member  160 . 
     The connection unit  133  may be provided at the end of the board connection unit  131  and arranged perpendicular to one end of the curvature piece  134  that is one side of the bare cell connection unit  132  in order to connect the board connection unit  131  to the bare cell connection unit  132 . 
     A secondary protective element may be provided between the first lead plate  130  and the protective circuit module  120 . A positive temperature coefficient (PTC) element  180  or a safety element having equivalent performance may be provided as the secondary protective element. According to an embodiment of the present invention, the PTC element  180  is used as the secondary protective element. However, a thermal fuse may be used as the secondary protective element. Although the secondary protective element is not provided, the battery pack according to an embodiment of the present invention may be carried out. 
     The second lead plate  140  may include a board connection unit  141  provided at one end and connected to the negative electrode connection terminal of the protective circuit board  121 , a bare cell connection unit  142  provided at the other end and connected to the electrode terminal  112  of the third surface  111   c  of the can  111  corresponding to the negative electrode terminal of the bare cell  110 , and a connection unit  143  connecting the board connection unit  141  to the bare cell connection unit  142 . 
     The board connection unit  141  may be parallel with the protective circuit board  121  and may be electrically connected to the negative electrode connection terminal of the protective circuit board  121  by welding or the like. 
     The bare cell connection unit  142  may have a shape matching the shape of the fifth surface  111   e  of the bare cell  110  including the can  111 . The bare cell connection unit  142  can include a curvature piece  144  having the same or similar curvature as that of the fifth surface  111   e  of the can  111  and a connector  145  bent from the curvature piece  144  at a right angle to be connected to the electrode terminal  112  that protrudes from the third surface  111   c  of the can  111 . The curvature piece  144  may have a larger width than the connection unit  145 . That is, the curvature piece  144  may have a large contact area with the fifth surface  111   e . Therefore, the area, of which the curvature piece  144  supports the protective circuit board  121 , may increase. The connector  145  may be connected to the electrode terminal  112  of the third surface  111   c  of the can  111  through a second through hole  162  of the insulation member  160 . That is, although the width of the connector  145  may be smaller than the width of the curvature piece  144 , any width, with which the connector  145  is electrically connected to the electrode terminal  112  of the third surface  111   c  by welding or the like, may be allowable. 
     Both ends of the connection unit  143  may be perpendicular to the board connection unit  141  and the bare cell connection unit  142 . 
     The cover  150  may surround the bare cell  110 , the protective circuit module  120 , and the first and second lead plates  130  and  140 . The cover  150  can include four frames  151 ,  152 ,  153 , and  154  integrated with each other. 
     The first frame  151  can correspond to the fifth surface  111   e  of the bare cell  110 . The first frame  151  may surround the protective circuit module  120 . The first frame  151  can have a plurality of terminal holes  151  a, through which the external terminals  122  of the protective circuit module  120  protrude. The first frame  151  may have a water-sensitive label attaching groove  151   b , to which a water-sensitive label  190  may be attached on the other side thereof. 
     The second frame  152  may be formed at one end of the first frame  151  to be integrated with the first frame  151 . The third frame  153  may be formed at the other end of the first frame  151  to be integrated with the first frame  151 . The second frame  152  may correspond to the third surface  111   c  of the can  111  and the third frame  153  may correspond to the fourth surface  111   d  of the can  111  so that the third and fourth surfaces  111   c  and  111   d  of the can  111  are protected. 
     Both ends of the fourth frame  154  may be integrated with the ends of the second frame  152  and the third frame  153 . Therefore, the fourth frame  154  may correspond to the fourth surface  111   d  of the can  111  to protect the fourth surface  111   d  of the can  111 . 
     The insulation member  160  may be attached to the third surface  111   c , the fourth surface  111   d , and the fifth surface  111   e  of the can  111 . The insulation member  160  may insulate the protective circuit element  123  of the protective circuit module  120  mounted on the fourth surface  111   d  from the can  111  of the bare cell  110 . The insulation member  160  may insulate the first lead plate  130  mounted on the fourth surface  111   d  and the second lead plate  140  mounted on the third surface  111   c  from the can  111  of the bare cell  110 . 
     The insulation member  160  may have a first through hole  161  formed in one side and a second through hole  162  formed in the other side. The connector  135  of the first lead plate  130  may be connected to the fourth surface  111   d  that is one surface of the can  111  corresponding to the positive electrode of the bare cell  110  by the first through hole  161 . The connector  145  of the second lead plate  140  may be connected to the electrode terminal  112  corresponding to the negative electrode of the bare cell  110  by the second through hole  162 . 
     A tape made of an insulation material or any member having the same property, material, and shape as the tape may be used as the insulation member  160 . 
     The label  170  may surround the sides and the bottom of the bare cell  110  after the bare cell  110  is coupled with the cover  150 . 
     Processes of assembling the battery pack  100  according to an embodiment of the present invention having the above structure will be described. 
     First, the first lead plate  130  and the second lead plate  140  may be assembled on the protective circuit board  121  of the protective circuit module  120 . That is, the board connection unit  131  of the first lead plate  130  may be welded to the positive electrode connection terminal (not shown) of the protective circuit board  121 . According to an embodiment of the present invention, a PTC element  180  may be mounted between the first lead plate  130  and the protective circuit board  121 . Therefore, a board connection unit  131  of the first lead plate  130  may be connected to one end of the PTC element  180 . The other end of the PTC element  180  may be connected to the positive electrode connection terminal of the protective circuit board  121 . 
     The negative electrode connection terminal (not shown) of the protective circuit board  121  may be welded to the board connection unit  141  of the second lead plate  140 . 
     Then, the first and second lead plates  130  and  140  are electrically connected to the bare cell  110 . 
     Before the first and second lead plates  130  and  140  are connected to the bare cell  110 , the insulation member  160  may be attached to the external surface of the bare cell  110 . The insulation member  160  may be attached to the third, fourth, and fifth surfaces  111   c ,  111   d , and  111   e  of the can  111 , to which the first and second lead plates  130  and  140  may be attached. 
     The protective circuit module  120 , in which the first and second lead plates  130  and  140  are assembled, may be seated on the narrow and relatively long fifth or sixth surface  111   e  or  111   f  among the sides of the can  111  of the bare cell  110 . According to an embodiment of the present invention, the protective circuit module  120  may be seated on the fifth surface  111   e.    
     The protective circuit module  120  may be seated such that the first and second lead plates  130  and  140  are electrically connected to mechanically support the protective circuit module  120 . 
     The curvature piece  134  of the bare cell connection unit  132  of the first lead plate  130  may be seated on the fifth surface  111   e . The connector  135  may be welded to the fourth surface  111   d . Therefore, the first lead plate  130  may be electrically connected to the positive electrode of the bare cell  110  by the connector  135 . The first lead plate  130  can mechanically support the protective circuit board  121  by the curvature piece  134 . In particular, the curvature piece  134  may have approximately the same curvature as that of the fifth surface  111   e  and a large width so that the curvature piece  134  may be closely attached to the fifth surface  111   e.    
     The curvature piece  144  of the bare cell connection unit  142  of the second lead plate  140  may be seated on the fifth surface  111   e . The connector  145  may be welded to the electrode terminal  112  as a negative electrode terminal that protrudes from the third surface  111   c . Therefore, the second lead plate  140  i may be s electrically connected to the negative electrode of the bare cell  110  by the connector  145 . The second lead plate  140  can mechanically and stably support the protective circuit board  121  by the curvature piece  144 . The curvature piece  144  may have approximately the same curvature as that of the fifth surface  111   e  and a large width so that the curvature piece  144  may be closely attached to the fifth surface  111   e.    
     As described above, the curvature pieces  134  and  144  of the first and second lead plates  130  and  140  may have the same curvature as that of the fifth surface  111   e  of the bare cell  110  and may have a relatively large width. Therefore, the curvature pieces  134  and  144  may have a large area and be attached to the fifth surface  111   e  of the bare cell  110 . Therefore, the protective circuit board  121  may be supported by the first and second lead plates  130  and  140  as stably as possible. 
     Then, the cover  150  can make the protective circuit module  120  surround the bare cell  110 . The first frame  151  of the cover  150  can surround parts of the protective circuit module  120  and the first and second lead plates  130  and  140 . The external terminals  122  of the protective circuit module  120  can protrude through the terminal holes  151   a  formed in the first frame  151 . The remaining parts of the first and second lead plates  130  and  140  may be surrounded by the second and third frames  152  and  153 . The fourth frame  154  may surround the sixth surface  111   f  of the bare cell  110 . 
     Finally, the bare cell  110  and the cover  150  may be surrounded by the label  170 . The cover  150  may be prevented from being separated from the bare cell  110  by the label  170 . 
     The water-sensitive label  190  may be attached to the first frame  151  of the cover  150 . 
     As described above, in a battery pack  100  according to an embodiment of the present invention, the first and second lead plates  130  and  140  may have the same curvature as that of one surface of the bare cell  110  to be attached thereto to support the protective circuit module  120  including the protective circuit board  121 . At this time, the first and second lead plates  130  and  140  may electrically connect the bare cell  110  to the protective circuit module  120  and mechanically support the protective circuit module  120 . Therefore, a separated support is not required. Although an external shock is applied thereto, the protective circuit module  120  may be stably supported by the first and second lead plates  130  and  140 . 
     Then, the battery pack  100  according to another embodiment of the present invention will be described in accordance with another view point. 
     Referring to  FIGS. 4 and 5 , in the battery pack  100  according to an embodiment of the present invention, the first and second lead plates  130  and  140  support the protective circuit module  120 . The first and second lead plates  130  and  140  can include the board connection units  131  and  141 , the bare cell connection units  132  and  142 , and the connection units  133  and  143  for connecting the board connection units  131  and  141  to the bare cell connection units  132  and  142 . 
     The height h of the connection units  133  and  143  may be equal to the height h 1  of the protective circuit element  123  mounted on the protective circuit board  121 . The protective circuit element  123  may be mounted in the center of the protective circuit board  121 . 
     In general, the protective circuit element  123  may be mounted on the surface opposite to the surface on which the external terminals  122  of the protective circuit board  121  are mounted. Therefore, the protective circuit element  123  can face one surface of the bare cell  110 . When the height h of the connection units  133  and  143  is equal to the height h 1  of the protective circuit element  123 , the protective circuit element  123  may support the protective circuit module  120  including the protective circuit board  121 . 
     In general, the protective circuit element  123  can have a height of about 1.0 mm. When the length h of the connection units  133  and  143  of the first and second lead plates  130  and  140  is equal to the height h 1  of the protective circuit element  123 , the first and second lead plates  130  and  140  and the protective circuit element  123  may support the protective circuit board  121  together. Therefore, the protective circuit board  121  may be stably supported by one surface of the bare cell  110 . 
     The protective circuit element  123  may be mounted approximately in the center of one surface of the protective circuit board  121 . Therefore, the protective circuit board  121  may be supported by the protective circuit element  123  to prevent from being bent at the center. 
     The curvature units  134  and  144  of the first and second lead plates  130  and  140  may have an area of at least 20% of the area of the fifth surface  111   e . According to an embodiment of the present invention, when the area of the fifth surface  111   e  is 312.149 mm 2 , the area of the curvature piece  134  of the first lead plate  130  is 40.744 mm 2  and the area of the curvature piece  144  of the second lead plate  140  is 20.7696 mm 2 . Therefore, the sum of the areas of the curvature pieces  134  and  144  of the first and second lead plates  130  and  140  of the area of the fifth surface  111   e  is about 19.7%. 
     When the areas of the curvature pieces of the first and second lead plates are remarkably smaller than ⅕ of the area of the fifth surface, it is difficult to stably support the protective circuit board. When the areas of the curvature pieces of the first and second lead plates are excessively larger than the area of the fifth surface, the fabrication cost of the lead plates increase and the assembly of the lead plates deteriorate. 
     In the above-described embodiment of the present invention, the first and second lead plates are connected to the bare cell by welding, but the connections are not limited thereto. That is, the first and second lead plates may be connected to the bare cell with an adhesive such as a tape. 
     As described above, in the battery pack according to an embodiment of the present invention, the center of the protective circuit board may be supported by the protective circuit element to prevent the protective circuit board from being bent. The first and second lead plates may be attached to one surface of the bare cell to support both ends of the protective circuit board. 
     Therefore, in the battery pack according to an embodiment of the present invention, the protective circuit module including the protective circuit board may be stably supported by the first and second lead plates so that fabrication costs spent in mounting a separated support may be reduced and assembling processes simplified.