Abstract:
A battery including an electrode assembly including a positive electrode, a negative electrode, and a separator therebetween; a case housing the electrode assembly; a cap plate coupled to the case; a collector plate coupled to the electrode assembly; and a terminal coupled to the collector plate and passing through the cap plate, wherein the terminal includes a terminal protrusion and a bottom protrusion, the collector plate includes an electrode region coupled to the electrode assembly and a terminal region coupled to the terminal, the terminal region including a combining hole passing therethrough, the combining hole having a noncircular shape, and the bottom protrusion of the terminal has an interengaging, matching shape relative to the combining hole, passes through the combining hole of the collector plate, and is welded to a lower surface of the collector plate.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    Embodiments relate to a rechargeable battery. 
         [0003]    2. Description of the Related Art 
         [0004]    A rechargeable battery, i.e., a secondary battery, may be repeatedly charged and discharged, unlike a primary battery that cannot be recharged. A rechargeable battery may be classified as a low-capacity battery or a high-capacity battery. A high-capacity secondary battery may be used to form a battery module by connecting a plurality of unit batteries in the form of a pack, and may be used as a power supply for driving motors in, e.g., hybrid electric vehicles and the like. 
         [0005]    A rechargeable battery module may acquire a desired power output by coupling a plurality of unit batteries in series. Each unit battery may include an electrode assembly having a positive electrode, a separator, and a negative electrode, a case in which the electrode assembly is installed, a cap plate coupled to the case and sealing an opening of the case, an electrode terminal having an insulation structure in a terminal hole of the cap plate, and a lead tab electrically connecting the electrode terminal to the electrode assembly. 
         [0006]    An insulation structure may be disposed in the terminal holes between the electrode terminals and the cap plate. The electrode terminal may be electrically connected to the lead tab by welding an end portion of the electrode terminal in an internal side of the cap plate to the lead tab. The electrode terminal may be fixed to the terminal hole of the cap plate by fastening a nut from an external side of the cap plate. 
         [0007]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it 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 
       [0008]    Embodiments are directed to a rechargeable battery, which represents advantages over the related art. 
         [0009]    It is a feature of an embodiment to provide a rechargeable battery that exhibits increased welding strength between an electrode terminal and a lead tab. 
         [0010]    It is another feature of an embodiment to provide a rechargeable that includes a stably fixed electrode terminal and lead tab after a welding process is performed. 
         [0011]    It is another feature of an embodiment to provide a rechargeable battery wherein minimal heat is generated when an electrode terminal and a lead tab are coupled. 
         [0012]    It is another feature of an embodiment to provide a rechargeable battery with lower production costs by having a structure that enables one-dimensional driving of a welding torch. 
         [0013]    At least one of the above and other features and advantages may be realized by providing a battery including an electrode assembly including a positive electrode, a negative electrode, and a separator therebetween; a case housing the electrode assembly; a cap plate coupled to the case; a collector plate coupled to the electrode assembly; and a terminal coupled to the collector plate and passing through the cap plate, wherein the terminal includes a terminal protrusion and a bottom protrusion, the collector plate includes an electrode region coupled to the electrode assembly and a terminal region coupled to the terminal, the terminal region including a combining hole passing therethrough, the combining hole having a noncircular shape, and the bottom protrusion of the terminal has an interengaging, matching shape relative to the combining hole, passes through the combining hole of the collector plate, and is welded to a lower surface of the collector plate. 
         [0014]    The bottom protrusion may be welded to the lower surface of the collector plate in a weld line around a circumference of the combining hole. 
         [0015]    The weld line may have a width, the width of the weld line being less than a width of the bottom protrusion. 
         [0016]    The combining hole may have a length and a width, the length of the combining hole being greater than the width. 
         [0017]    The bottom protrusion may be welded to the lower surface of the collector plate in a weld line along the length of the bottom protrusion. 
         [0018]    The weld line may have a width, the width of the weld line being about the same as the width of the bottom protrusion. 
         [0019]    The combining hole may have a depth, the bottom protrusion may have a height, and the depth of the combining hole may be about the same as the height of the bottom protrusion. 
         [0020]    The terminal may further include a flange between the bottom protrusion and the terminal protrusion. 
         [0021]    The terminal may have a longitudinal axis and the noncircular shape of the combining hole may be in a plane transverse to the axis. 
         [0022]    At least one of the above and other features and advantages may also be realized by providing a battery including an electrode assembly including a positive electrode, a negative electrode, and a separator therebetween; a case housing the electrode assembly; a cap plate coupled to the case; a collector plate coupled to the electrode assembly; and a terminal coupled to the collector plate and passing through the cap plate, wherein the terminal includes a terminal protrusion and a bottom protrusion, the collector plate includes an electrode region coupled to the electrode assembly and a terminal region coupled to the terminal, the terminal region including a combining hole passing therethrough, and the bottom protrusion of the terminal has an interengaging, matching shape relative to a shape of the combining hole, passes through the combining hole of the collector plate, and is welded to a lower surface of the collector plate, wherein the lower surface of the collector plate includes a protruded region around the combining hole and the combining hole passes through the protruded region. 
         [0023]    The bottom protrusion may be welded to the lower surface of the collector plate in a weld line around a circumference of the combining hole. 
         [0024]    The weld line may have a width, the width of the weld line being less than a width of the bottom protrusion. 
         [0025]    The combining hole may have a length and a width, the length of the combining hole being greater than the width. 
         [0026]    The bottom protrusion may be welded to the lower surface of the collector plate in a weld line along the length of the bottom protrusion. 
         [0027]    The weld line may have a width, the width of the weld line being about the same as the width of the bottom protrusion. 
         [0028]    The combining hole may have a depth, the bottom protrusion may have a height, and the height of the bottom protrusion may be about equal to the depth of the combining hole. 
         [0029]    The terminal may further include a flange between the bottom protrusion and the terminal protrusion. 
         [0030]    The combining hole may have a noncircular shape. 
         [0031]    The terminal may have a longitudinal axis and the noncircular shape of the combining hole may be in a plane transverse to the axis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    The above and other features and advantages will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, in which: 
           [0033]      FIG. 1  illustrates a perspective view of a rechargeable battery according to an embodiment; 
           [0034]      FIG. 2  illustrates a cross-sectional view of the rechargeable battery of  FIG. 1 , taken along the line II-II; 
           [0035]      FIG. 3  illustrates an exploded perspective view of an electrode terminal and a collector plate of  FIG. 2 ; 
           [0036]      FIG. 4  illustrates a cross-sectional view of the electrode terminal and the collector plate  FIG. 3  in an assembled state, taken along IV-IV; 
           [0037]      FIG. 5  illustrates a bottom view of the collector plate of  FIG. 4 ; 
           [0038]      FIG. 6  illustrates a cross-sectional view of an electrode terminal and a collector plate of a rechargeable battery according to another embodiment; 
           [0039]      FIG. 7  illustrates a bottom view of the collector plate of  FIG. 6 ; 
           [0040]      FIG. 8  illustrates an exploded perspective view of an electrode terminal and a collector plate of a rechargeable battery according to yet another embodiment; 
           [0041]      FIG. 9  illustrates a cross-sectional view of the electrode terminal and the collector plate of  FIG. 8 , taken along the line IX-IX; 
           [0042]      FIG. 10  illustrates a bottom view of the collector plate of  FIG. 9 ; 
           [0043]      FIG. 11  illustrates a cross-sectional view of an electrode terminal and a collector plate of a rechargeable battery according to still another embodiment; and 
           [0044]      FIG. 12  illustrates a bottom view of the collector plate of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0046]    In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another element, it can be directly on the other element, or intervening elements may also be present. In addition, it will also be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout. 
         [0047]      FIG. 1  illustrates a perspective view of a rechargeable battery according to a first embodiment.  FIG. 2  illustrates a cross-sectional view of the rechargeable battery of  FIG. 1 , taken along the line II-II. 
         [0048]    Referring to  FIG. 1  and  FIG. 2 , a rechargeable battery  100  may include a case  20  in which an electrode assembly  10  may be installed. The rechargeable battery  100  may also include a cap plate  30  sealing an opening in a side of the case  20 , electrode terminals  41  and  42  disposed in terminal holes  311  and  312  of the cap plate  30 , and lead tabs, i.e., collector plates,  501  and  502  connecting the electrode terminals  41  and  42  to the electrode assembly  10 . 
         [0049]    The electrode assembly  10  may include a positive electrode  11 , a negative electrode  12 , and an insulating separator  13 . The positive electrode  11  and the negative electrode  12  may be disposed on respective sides of the separator  13 . The electrode assembly  10  may be formed in jelly-roll structure by spirally winding the positive electrode  11  and the negative electrode  12  with the separator  13  therebetween. 
         [0050]    The positive electrode  11  and the negative electrode  12  may respectively include a current collector and an active material coated on a portion of a surface of the current collector. The current collector may be formed of, e.g., a thin metal foil. In addition, the positive electrode  11  and the negative electrode  12  may respectively include a coated region including portions of the current collector coated with the active material and uncoated regions  111  and  121  including portions of the current collector not coated with the active material. 
         [0051]    The coated region may occupy almost an entire area of each of the positive electrode  11  and the negative electrode  12 . The uncoated regions  111  and  121  in an electrode assembly  10  having a jelly roll structure may be disposed at respective sides of the coated region. 
         [0052]    The electrode assembly  10  may include wide front and rear areas in the jelly roll structure. End portions of the uncoated regions  111  and  121 , which may be, e.g., left and right sides of the uncoated regions  111  and  121 , may be formed in a shape that substantially corresponds to a cuboid having a narrow and long area. 
         [0053]    The case  20  may form an entire exterior of the rechargeable battery  100 . The case  20  may be formed of a conductive metal, e.g., aluminum, an aluminum alloy, and/or nickel-plated steel. 
         [0054]    In addition, the case  20  may provide a space for installing the electrode assembly  10  therein. In an implementation, the case  20  may be formed in, e.g., a prismatic hexahedron having an opening in one side thereof for receiving the electrode assembly  10  in a shape that corresponds to a hexahedron. The opening may face upward in the case  20 , as illustrated in  FIG. 1  and  FIG. 2 . 
         [0055]    The cap plate  30  have a thin plate structure. The cap plate  30  may be coupled to the opening to close and seal the case  20 . The cap plate  30  may connect, e.g., both inside and outside the case  20 , as necessary, while blocking the inside and outside of the case  20 . 
         [0056]    The cap plate  30  may include constituent elements for forming and operation of the rechargeable battery  100 . In particular, the cap plate  30  may include, e.g., terminal holes  311  and  312  for the electrode terminals  41  and  42  to pass through, an electrolyte injection opening  32  for injection of an electrolyte solution, and a vent hole  35  for relieving pressure of the rechargeable battery  100  when internal pressure is excessively increased. 
         [0057]    The electrolyte injection opening  32  may facilitate injection of the electrolyte solution into the case  20  after the case  20  is coupled to the cap plate  30 . After the injection of the electrolyte solution into the case  20 , the electrolyte injection opening  32  may be sealed by the sealing cap  33 . 
         [0058]    During normal operation of the rechargeable battery  100 , the vent hole  35  may be maintained in a closed state, i.e., the vent hole  35  may be closed and sealed by the vent plate  34 , only to be opened when an internal pressure is excessively increased. That is, the vent plate  34  may be a thinner plate than the cap plate  30  and may be coupled to the cap plate  30  around the vent hole  35 . 
         [0059]    When the internal pressure of the case  20  increases above a predetermined level due to, e.g., a malfunction during charging and discharging of the electrode assembly  10 , the vent plate  34  may burst due to the internal pressure. Thus, internal gases of the rechargeable battery  100  may be emitted. In turn, explosion of the rechargeable battery  100  may be prevented. 
         [0060]    The terminal holes  311  and  312  may penetrate the cap plate  30  so as to facilitate insertion of the electrode terminals  41  and  42  therethrough. That is, the electrode terminals  41  and  42  may respectively electrically connect the positive electrode  11  and the negative electrode  12  of the electrode assembly  10  to an outside of the battery  100  through the terminal holes  311  and  312 . 
         [0061]    The electrode terminals  41  and  42  may be respectively inserted through the terminal holes  311  and  312  by providing an outer insulator  43  and an inner insulator  44  therebetween. The outer insulator  43  and the inner insulator  44  may form an electrical insulation structure in the terminal holes  311  and  312  between the electrode terminals  41  and  42  and the cap plate  30 . 
         [0062]    The electrode terminals  41  and  42  may be electrically connected to the electrode assembly  10  inside the case  20 , may pass through the terminal holes  311  and  312 , and may simultaneously protrude outside the case  20 . The electrode terminals  41  and  42  may include a positive electrode terminal  41  connected to the positive electrode  11  and a negative electrode terminal  42  connected to the negative electrode  12 . 
         [0063]    Ends of the collector plates  501  and  502  may be respectively connected to the electrode terminals  41  and  42 . Other ends of the collector plates  501  and  502  may be respectively connected to the uncoated regions  111  and  121  at ends of the electrode assembly  10 . That is, the collector plates  501  and  502  may be formed as a pair, e.g., having a symmetrical structure, and may respectively connect the positive electrode  11  and the negative electrode  12  to the positive electrode terminal  41  and the negative electrode terminal  42  in the same manner. 
         [0064]    For convenience, a coupled structure of the positive electrode terminal  41  and the collector plate  501  will be exemplarily described for coupling structures of the collector plates  501  and  502  and the respective electrode terminals  41  and  42 . 
         [0065]      FIG. 3  illustrates an exploded perspective view of the terminal electrode and the lead tab of  FIG. 2 . Referring to  FIG. 3 , the positive electrode terminal  41  may include a stem, i.e., a terminal protrusion,  61  inserted through a terminal hole  311  and protruding outside of the cap plate  30 , a flange  62  disposed at an end of the terminal protrusion  61 , and a bottom protrusion  63  protruding from the flange  62  opposite to the terminal protrusion  61 . 
         [0066]    The collector plate  501  may include a horizontal region, i.e., a terminal region  51 , coupled to the flange  62  of the positive electrode terminal  41 , a penetrating combining hole  52  in the terminal region  51  into which the bottom protrusion  63  may be inserted, and a vertical region, i.e., an electrode region  53 , extended in a vertical direction (i.e., z-axis direction) from the terminal region  51  and connected to the uncoated region  111  of the electrode assembly  10 . 
         [0067]      FIG. 4  illustrates a cross-sectional view of the electrode terminal and the lead tab of  FIG. 3  in an assembled state, taken along the line IV-IV.  FIG. 5  illustrates a bottom view of the lead tab of  FIG. 4 . 
         [0068]    Referring to  FIG. 4  and  FIG. 5 , the flange  62  of the positive electrode terminal  41  may contact the terminal region  51  of the collector plate  501 . The bottom protrusion  63  may be inserted into the combining hole  52 . Then, the bottom protrusion  63  may be welded to the terminal region  51  along an edge of the combining hole  52 . In an implementation, the bottom protrusion  63  may be welded around a circumference of the combining hole  52 . In another implementation, the bottom protrusion  63  may be welded to the collector plate  501  using, e.g., Tungsten Inert Gas (TIG) welding. 
         [0069]    The flange  62  may increase a contact area between the positive electrode terminal  41  and the terminal region  51 , thereby improving an electrical connection and reducing electrical resistance therebetween. The bottom protrusion  63  may increase a contact area with the combining hole  52  by being inserted and interengaged therein. Accordingly, electrical resistance between the positive electrode terminal  41  and the collector plate  501  may be further reduced. 
         [0070]    A weld line W 1  may be formed along an exterior circumference of the bottom protrusion  63  and an interior circumference of the combining hole  53 . Due to an interengaging, matching shape of the bottom protrusion  63  and the combining hole  53 , the exterior circumference of the bottom protrusion  63  and the interior circumference of the combining hole  53  may be congruent. The weld line W 1  may form a closed curved line and may increase a welding length of the positive electrode terminal  41  and the collector plate  501  to thereby increase welding strength thereof. Since the bottom protrusion  63  and the combining hole  52  may be interengaged prior to welding the positive electrode terminal  41  and the collector plate  501 , welding strength therebetween may be further increased. 
         [0071]    A length of the bottom protrusion  63  in a first direction (x-axis direction of  FIG. 5 ) and a length of the bottom protrusion  63  in a second direction (y-axis direction of  FIG. 5 ) may be different from each other. For example, a first length L 1  in the x-axis direction of the bottom protrusion  63  may be larger than a second length L 2  of the bottom protrusion  63  in the y-axis direction. In an implementation, the bottom protrusion may have an interengaging, matching shape relative to the combining hole  52 . In another implementation, the bottom protrusion  63  and the combining hole  52  may have a noncircular shape. Further, the positive electrode terminal  41  including the bottom protrusion  63  may have a longitudinal axis and the noncircular shape of the combining hole  52  may be in a plane transverse to the axis. 
         [0072]    In the terminal region  51  of the collector plate  501 , the combining hole  52  may have the first length L 1  in the x-axis direction and the second length L 2  in the y-axis direction. The bottom protrusion  63  may have the interengaging, matching shape, i.e., may have the same first length L 1  and second length L 2 , and may be stably inserted into the combining hole  52 . 
         [0073]    The combining hole  52  may have different directivity with respect to the x-axis direction and the y-axis direction. In other words, as described above, the first length L 1  may be different from the second length L 2 . When the bottom protrusion  63  is inserted to the combining hole  52 , the first and second lengths L 1  and L 2 , being different in size, may advantageously prevent rotation of the positive electrode terminal  41  in the terminal hole  311  when coupling unit batteries. In other words, when coupling multiple rechargeable batteries by fastening a nut  45  to the terminal protrusion  61 , the positive electrode terminal  41  may not rotate because of the shapes of the bottom protrusion  63  and the combining hole  52 . 
         [0074]    Hereinafter, other embodiments will be described in further detail. Repeated description of parts that are the same as that of the previous embodiment will be omitted. 
         [0075]      FIG. 6  illustrates a cross-sectional view of an electrode terminal and a lead tab of a rechargeable battery according to another embodiment.  FIG. 7  illustrates a bottom view of the collector plate of  FIG. 6 . 
         [0076]    The terminal region  51  of the collector plate  50  of the previous embodiment may simply include the combining hole  52 . However, a terminal region  251  of a collector plate  250  of the present embodiment may include a combining hole  252  and may further include a protruded region  254  having an increased thickness around the combining hole  252 . In other words, the protruded region  254  may be disposed around the combining hole  252  where a thickness of the terminal region  251  is greater than other regions of the terminal region  251 . That is, the combining hole  252  may be deeper than the combining hole  52  of the previous embodiment by a height of the protruded region  252 . 
         [0077]    The collector plate  250  may include a first surface S 1  that contacts a flange  262  and a second surface S 2  parallel to and opposite to the first surface S 1 . The protruded region  254  may protrude from the second surface S 2  of the terminal region  251 . The protruded region  254  may further increase stiffness of the collector plate  250  around the combining hole  252 . 
         [0078]    The combining hole  252  may have a depth D that is equal to a sum of a thickness T of the terminal region  251  and a height H of the protruded region  254 . In addition, a bottom protrusion  263  of the positive electrode terminal  241  may be inserted into and interengage the combining hole  252 . Accordingly, the bottom protrusion  263  may be longer than the bottom protrusion  63  of the previous embodiment by the height H of the protruded region  254 . That is, a length L of the bottom protrusion  263  may equal the sum (i.e., L=T+H=D) of the thickness T of the terminal region  251  and the height H of the protruded region  254 . 
         [0079]    Compared to the previous embodiment, the depth D of the combining hole  252  may be deeper and the length L of the bottom protrusion  263  of the positive electrode terminal  241 , corresponding to the depth D, may be greater in the present embodiment. Therefore, the bottom protrusion  263  may be inserted into, and interengage with, the combining hole  252  and may further increase a contact area therebetween, compared to the previous embodiment. Therefore, electrical resistance between the positive electrode terminal  241  and the collector plate  250  may be further decreased. 
         [0080]    A closed curved weld line W 2  formed along the combining hole  252  and the bottom protrusion  263  may increase a welding length of the positive electrode terminal  241  and the collector plate  250 , as in the previous embodiment, to thereby enhance welding strength. 
         [0081]    In addition, a contact area of the bottom protrusion  263  and the combining hole  252  may be greater by an area corresponding to the height H of the protruded region  254 . As described above, the weld line W 2  may further increase the welding strength between the positive electrode terminal  241  and the collector plate  250 . When the rechargeable batteries  100  are coupled to one another, rotation of the positive electrode terminal  241  in the terminal hole  31  may be further prevented. 
         [0082]      FIG. 8  illustrates an exploded perspective view of an electrode terminal and a collector plate of a rechargeable battery according to yet another embodiment.  FIG. 9  illustrates a cross-sectional view of an assembled state of the electrode terminal and the collector plate of  FIG. 8 , taken along the line IX-IX.  FIG. 10  illustrates a bottom view of the collector plate of  FIG. 9 . 
         [0083]    In a previous embodiment, the combining hole  52  and the bottom protrusion  63  may have the second length L 2  (in the y-axis direction) larger than a width LW of the closed curved weld line W 1 . However, as illustrated in  FIG. 8  to  FIG. 10 , a first length L 31  (in the x-axis direction) of a bottom protrusion  363  of a positive electrode terminal  341 , may be much greater than a second length L 32  (in the y-axis direction) in the present embodiment. 
         [0084]    A combining hole  352  in a terminal region  351  of a collector plate  350  may have the first length L 31  (in the x-axis direction) and the second length L 32  (in the y-axis direction) for insertion and interengaging of the similarly-sized bottom protrusion  363  of the positive electrode terminal  341  therein. 
         [0085]    The second length L 32  of the combining hole  352  and the bottom protrusion  363  may be equal to a width LW 3  of a weld line W 3 . Such a configuration may allow the weld line W 3  to be formed as a straight line. Forming the weld line W 3  in a straight line may advantageously allow the weld line to be formed by a 2-axis driven welding device, as will be described below. 
         [0086]    Since the weld lines W 1  and W 2  of the previous embodiments may be formed as close curved-lines, a 3-axis driven welding device (not shown) that moves on a two-dimensional trajectory corresponding to the weld lines W 1  and W 2 , may be required. 
         [0087]    However, as noted above, the weld line W 3  having the width LW 3  may be formed in a straight line in the present embodiment. Therefore, a 2-axis driven welding device (not shown) that moves on a one-dimensional trajectory corresponding to the weld line W 3  may be used. Such a 2-axis driven welding device may be simpler to control and less expensive to operate than a 3-axis driven welding device. Accordingly, a welding process, and overall manufacturing process for the rechargeable battery, may be simplified, thereby reducing time and cost required to produce the rechargeable battery. 
         [0088]    In other words, the bottom protrusion  363  of the positive electrode terminal  341  and the combining hole  352  of the collector plate  350  may each have a second length L 32  corresponding to the weld line W 3 . The bottom protrusion  363  and the combining hole  352  may be interengaged and then welded in a single line, thereby simplifying the welding process therebetween. 
         [0089]      FIG. 11  illustrates a cross-sectional view of an electrode terminal and a collector plate of a rechargeable battery according to still another embodiment.  FIG. 12  illustrates a bottom view of the collector plate of  FIG. 11 . 
         [0090]    The terminal region  351  of the collector plate  350  of the previous embodiment may simply include the combining hole  352 . However, a terminal region  451  of a collector plate  450  according to the present embodiment may include a combining hole  452  and may further include a protruded region  454  having an increased thickness around the combining hole  452 . In other words, the protruded region  454  may be disposed around the combining hole  452  where a thickness of the terminal region  451  is greater than other regions of the terminal region  451 . That is, the combining hole  452  may be deeper than the combining hole  352  of the previous embodiment by a height of the protruded region  454 . 
         [0091]    The collector plate  450  may include a first surface S 1  that contacts a flange  462  and a second surface S 2  parallel and opposite to the first surface S 1 . The protruded region  454  may protrude from the second surface S 2  of the terminal region  451 . The protruded region  454  may further increase stiffness of the collector plate  450  around the combining hole  452 . 
         [0092]    The combining hole  452  may have a depth D that is equal to a sum of a thickness T of the terminal region  451  and a height H of the protruded region  454 . In addition, a bottom protrusion  463  of the positive electrode terminal  441  may be inserted into, and interengage with, the combining hole  452 . Accordingly, the bottom protrusion  463  may be longer than the bottom protrusion  363  of the previous embodiment by the height H of the protruded region  454 . That is, a length L of the bottom protrusion  463  may equal the sum (i.e., L=T+H=D) of the thickness T of the terminal region  451  and the height H of the protruded region  454 . 
         [0093]    Compared to the previous embodiment, the depth D of the combining hole  452  may be deeper and the length L of the bottom protrusion  463  of the positive electrode terminal  441 , corresponding to the depth D, may be greater in the present embodiment. Therefore, the bottom protrusion  463  may be inserted into, and interengage with, the combining hole  452  and may further increase a contact area therebetween, compared to the previous embodiment. Therefore, electrical resistance between the positive electrode terminal  441  and the collector plate  450  may be further decreased. 
         [0094]    As described above, a straight weld line W 4  formed along the combining hole  452  and the bottom protrusion  463  may increase a welding length of the positive electrode terminal  441  and the collector plate  450 , as in the previous embodiment, to thereby increase welding strength. 
         [0095]    In addition, a contact area of the bottom protrusion  463  and the combining hole  452  may be increased by an area corresponding to the height H of the protruded region  454 . Further, the weld line W 4  may further increase the welding strength of the positive electrode terminal  441  and the collector plate  450 . Accordingly, when the rechargeable batteries  100  are coupled, rotation of the positive electrode terminal  441  in a terminal hole  31  may be further prevented. 
         [0096]    The foregoing embodiments avoid a construction featuring a face-to-face coupling of an inward end portion of the electrode terminal and the collector laser-welded at a side between the inward end portion and the collector plate. Accordingly, the embodiments also avoid the drawbacks of such an arrangement, mainly, that the welding strength between the inward end portion and the collector plate may be inefficient, and the electrode terminal may protrude due to the welding. 
         [0097]    As described above, according to an embodiment, a combining hole may be formed in a terminal region of a collector plate, a bottom protrusion may be formed in an electrode terminal, and the collector plate and the electrode terminal may be welded in a state that the bottom protrusion is inserted into the combining hole so that welding strength between the electrode terminal and the collector plate may be increased. 
         [0098]    A protruded region may be further formed around the combining hole so that the electrode terminal and the collector plate may be stably maintained in position after the welding process by preventing thermal deformation of the collector plate and the electrode terminal. 
         [0099]    A protruded region may be formed in the collector plate to increase the depth of the combining hole and the length of the bottom protrusion, corresponding to the depth, may also be increased to further increase welding strength, and electrical resistance may be beneficially lowered. 
         [0100]    The combining hole of the collector plate and the bottom protrusion of the electrode terminal may be linearly formed to form a straight weld line to thereby minimize heat generation during the welding process and simplify driving of a welding device. 
         [0101]    Exemplary embodiments 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 purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.