Abstract:
A rechargeable battery is provided, which can prevent incompatibility of rechargeable batteries with existing charging/discharging equipment by extending an electrode terminal to the center of a cap plate. In one exemplary embodiment, the rechargeable battery includes an electrode assembly including a positive electrode tab and a negative electrode tab, a can accommodating the electrode assembly, a cap plate sealing a top opening of the can and having a terminal through-hole at a first location offset toward one side of the cap plate with respect to the center of the cap plate, and an electrode terminal inserted into the terminal through-hole, wherein the electrode terminal extends along a top surface of the cap plate from the first location to the center of the cap plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0082114, filed on Aug. 24, 2010 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Aspects of embodiments according to the present invention relate to a rechargeable battery. 
         [0004]    2. Description of Related Art 
         [0005]    An exemplary lithium-ion battery includes a protective device, such as a positive temperature coefficient (PTC) device or a thermal fuse for protecting a temperature rise when the internal temperature of a battery abnormally increases due to an abnormality of the battery. The protective device may be positioned outside the battery. In such a case, however, the sensitivity of detecting heat generated inside the battery may be lowered. To overcome this, a structure in which a protective device that can be inserted into a battery has been developed. 
         [0006]    In order to facilitate installation of the protective device, a structure for shifting a position of an electrode terminal from the center to a side of the battery has been proposed. However, when a large-capacity battery is accommodated in a battery tray and undergoes charge/discharge processes, such a shift in position of the electrode terminal (to accommodate the protective device) may make it difficult to utilize existing charge/discharge equipment. This is because existing charge/discharge equipment may be configured to provide a charge/discharge plug on an electrode terminal positioned at the center of a cap plate of the battery. Accordingly, this may lead to undesirably lowering compatibility of rechargeable batteries with existing charge/discharge equipment. 
       SUMMARY 
       [0007]    To address the aforementioned problems, aspects of embodiments according to the present invention provide a rechargeable battery that is compatible with existing charging/discharging equipment while forming an electrode terminal at a location biased (for example, offset) toward one side of the center of a top surface of a cap plate. 
         [0008]    According to an exemplary embodiment of the present invention, a rechargeable battery is provided. The rechargeable battery includes an electrode assembly including a positive electrode tab and a negative electrode tab, a can accommodating the electrode assembly, a cap plate sealing a top opening of the can and having a terminal through-hole at a first location offset toward one side of the cap plate with respect to a center of the cap plate, and an electrode terminal inserted into the terminal through-hole. The electrode terminal extends along a top surface of the cap plate from the first location to the center of the cap plate. 
         [0009]    The electrode terminal may include a head portion extending along the top surface of the cap plate and a pillar portion inserted into the terminal through-hole. The head portion may extend past the center of the cap plate. 
         [0010]    The rechargeable battery may further include a terminal plate below the first location and electrically connected to the electrode terminal, and an insulation plate between a bottom surface of the cap plate and the terminal plate. 
         [0011]    The rechargeable battery may further include a protective device attached to a bottom surface of the insulation plate, where one side of the protective device is electrically connected to the terminal plate by a first connection tab, and another side of the protective device is electrically connected to the negative electrode tab by a second connection tab. 
         [0012]    The rechargeable battery may further include a heat blocking plate between the insulation plate and the protective device. 
         [0013]    The rechargeable battery may further include a second insulation plate on the bottom surface of the cap plate and a second terminal plate on a bottom surface of the second insulation plate. The second insulation plate is below a second location of the cap plate, the second location being offset toward an other side of the cap plate with respect to the center of the cap plate, the center of the cap plate being between the first location and the second location. 
         [0014]    The rechargeable battery may further include a protective device on the bottom surface of the second insulation plate, where one side of the protective device is electrically connected to the bottom surface of the cap plate by a first connection tab, an other side of the protective device is electrically connected to the second terminal plate by a second connection tab, and the second terminal plate is electrically connected to the positive electrode tab. 
         [0015]    The rechargeable battery may further include an insulation plate below the first location and on a bottom surface of the cap plate, and a protective device on a bottom surface of the insulation plate and electrically connected to the electrode terminal and the negative electrode tab. 
         [0016]    The rechargeable battery may further include an insulation gasket between the electrode terminal and the cap plate, where the insulation gasket is sized and shaped to fit the electrode terminal. 
         [0017]    The rechargeable battery may further include a protective device inside the can and electrically connected to the electrode terminal and one of the negative electrode tab or the positive electrode tab. 
         [0018]    The protective device may include a thermal fuse, a positive temperature coefficient element, or a bimetal. 
         [0019]    The protective device may include the thermal fuse. 
         [0020]    The rechargeable battery may further include a protective device inside the can and electrically connected to one of the negative electrode tab or the positive electrode tab, where the electrode terminal is electrically connected to an other of the negative electrode tab or the positive electrode tab. 
         [0021]    The protective device may include a thermal fuse, a positive temperature coefficient element, or a bimetal. 
         [0022]    The protective device may include the thermal fuse. 
         [0023]    As described above, a rechargeable battery according to embodiments of the present invention can solve or lessen the problem associated with forming a protective device inside the battery (for example, to make the protective device more sensitive to a change in the internal temperature of the battery). Since the electrode terminal is formed at a location biased to one side of the center of the cap plate, it is possible to prevent or lessen the incompatibility of the rechargeable battery with existing charging/discharging equipment. 
         [0024]    Additional aspects and/or features of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Features and aspects of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
           [0026]      FIG. 1  is a perspective view illustrating a bare cell of a rechargeable battery according to an embodiment of the present invention; 
           [0027]      FIG. 2A  is a partial sectional view of an electrode terminal and an insulation gasket, viewed from the direction ‘A’ of  FIG. 1 , and  FIG. 2B  is a top view viewed from the direction ‘C’ of  FIG. 1 ; 
           [0028]      FIG. 3  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell of a rechargeable battery according to an embodiment of the present invention; 
           [0029]      FIG. 4  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell of a rechargeable battery according to another embodiment of the present invention; 
           [0030]      FIG. 5  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell of a rechargeable battery according to yet another embodiment of the present invention; and 
           [0031]      FIG. 6  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell of a rechargeable battery according to still another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0033]      FIG. 1  is a perspective view illustrating a bare cell of a rechargeable battery according to an embodiment of the present invention.  FIG. 3  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell  100  of a rechargeable battery according to an embodiment of the present invention. 
         [0034]    Referring to  FIGS. 1 and 3 , the bare cell  100  of a rechargeable battery includes a can  200 , an electrode assembly  210  housed (or accommodated) inside the can  200 , and a cap assembly  300   a  sealing a top opening of the can  200 . The can  200  may be made of a metallic member having substantially a rectangular parallelepiped shape and may serve as a terminal. A top end of the can  200  may be open, forming a top opening, and the electrode assembly  210  can be inserted into the top opening of the can  200 . 
         [0035]    Referring to  FIG. 3 , the electrode assembly  210  includes a positive electrode plate  211 , a negative electrode plate  213 , and a separator  212  for separating the positive electrode plate  211  from the negative electrode plate  213 . The electrode assembly  210  can be produced, for example, by winding the positive electrode plate  211 , the separator  212 , the negative electrode plate  213 , and another separator  212  into a jelly roll-type structure. The positive electrode plate  211  has a positive electrode tab  150  welded thereto, and one end of the positive electrode tab  150  protrudes upward from the electrode assembly  210 . 
         [0036]    The cap assembly  300   a  includes a cap plate  310   a,  an electrode terminal  320 , and a protective device  330   a.  The cap plate  310   a  is made, for example, of a metal plate, sized and shaped to fit the top opening of the can  200  (to seal the top opening of the can  200 ). A terminal through-hole  311   a  is formed at a location (for example, a predetermined location) biased (for example, offset) to one side  301  from a center of the cap plate  310   a  (the center corresponding to a mid place between the one side  301  and an other side  302  of the cap plate  310   a ). The electrode terminal  320  can be inserted into the terminal through-hole  311   a  in a thickness direction of the cap plate  310   a  ranging from its top surface  304  to its bottom surface  303 . 
         [0037]    The electrode terminal  320 , for example, a negative terminal, is inserted into the terminal through-hole  311   a.  An electrolyte injection hole  312  having a size (for example, a predetermined size) is formed at a location biased to the other side  302  from the center of the cap plate  310   a.  An electrolyte is injected in a thickness direction of the cap plate  310   a  through the electrolyte injection hole  312 . A negative electrode tab  140  of the electrode assembly  210  is welded to the center of the bottom surface  303  of the cap plate  310   a  (with an insulation plate  313  therebetween), while the positive electrode tab  150  of the electrode assembly  210  is welded to the other side  302  of the cap plate  310   a.    
         [0038]    The electrode terminal  320  includes a head portion  321  exposed to the top surface of the cap plate  310   a,  and a pillar portion  322  inserted into the terminal through-hole  311   a.  In addition, an insulation gasket  340  is provided between the cap plate  310   a  and the electrode terminal  320  for electrical insulation therebetween. The insulation gasket  340  is sized and shaped to fit the electrode terminal  320 . 
         [0039]      FIGS. 2A and 2B  are partial sectional views of the electrode terminal  320  and the insulation gasket  340 , viewed from the directions ‘A’ and ‘C’, respectively, of  FIG. 1 . 
         [0040]    Referring to  FIG. 2A , when viewed from the front (in the direction ‘A’ of  FIG. 1 ), the electrode terminal  320  is bilaterally asymmetrical with respect to a centerline L, the centerline L being equidistant from one side  322   a  and an other side  322   b  of the pillar portion  322 , which is inserted into the terminal through-hole  311   a.  Thus, the electrode terminal  320  is constructed such that a distance ranging from one side  321   a  of the head portion  321  (upwardly protruding from the cap plate  310   a ) to the centerline L is shorter than a distance ranging from an other side  321   b  of the head portion  321  to the centerline L. In addition, the insulation gasket  340  is also shaped such that a distance ranging from one side  341  to the centerline L is shorter than a distance ranging from an other side  342  to the centerline L. 
         [0041]    Referring to  FIG. 2B , when viewed from the top (in the direction ‘C’ of  FIG. 1 ), the electrode terminal  320  (of which the head portion  321  is shown in  FIG. 2B ) is constructed to pass a centerline N (of the cap plate  310   a ), the centerline N being equidistant from the one side  301  and the other side  302  of the cap plate  310   a.  That is, the other side  321   b  of the head portion  321  extends toward the other side  302  of the cap plate, so that the head portion  321  passes the center of the cap plate  310   a.    
         [0042]    In this case, the distance ranging from the one side  321   a  of the head portion  321  to the centerline N and the distance ranging from the other side  321   b  of the head portion  321  to the centerline N may be greater than a width of a portion of a charge/discharge plug that contacts the top surface of the head portion  321  of the electrode terminal  320  during a formation process (that is, coupling the charge/discharge plug to the top surface of the head portion). This is to help insure good contact of the charge/discharge plug and the electrode terminal  320 . Here, the portion of the charge/discharge plug contacting the top surface of the head portion  321  is to be defined as a ‘charge/discharge plug end’ hereinafter. A purpose of the charge/discharge plug end is to safely connect the charge/discharge plug to the electrode terminal  320 . The insulation gasket  340  is also constructed to pass the centerline N as described above. 
         [0043]    Referring back to  FIG. 3 , a terminal plate  314  is electrically connected to the electrode terminal  320  (at the pillar portion  322 ) and is formed at a lower portion of a location biased toward the one side  301  of the cap plate  310   a.  The insulation plate  313  is formed between the bottom surface  303  of the cap plate  310   a  and the terminal plate  314  for electrically insulating the terminal plate  314  and the cap plate  310   a.  A polypropylene (PP) tape may be used, for example, as the insulation plate  313 . In addition, the electrode terminal  320  may serve as a positive electrode terminal to then be connected to the positive electrode tab  150 . 
         [0044]    The protective device  330   a  is electrically connected to the terminal plate  314  by a first connection tab  315  on one side of the protective device  330   a.  This also electrically connects the protective device  330   a  to the electrode terminal  320  since the terminal plate is electrically connected to the electrode terminal  320 . In addition, the first connection tab  315  also serves to attach the protective device  330   a  to a bottom surface of the insulation plate  313  that is positioned on the bottom surface  303  of the cap plate  310   a.  The protective device  330   a  is electrically connected to the negative electrode tab  140  by a second connection tab  316  at another side of the protective device. In other embodiments, the first connection tab  315  and the second connection tab  316  formed at the one side and the other side of the protective device  330   a  may be formed as a single element or integrally formed with the protective device  330   a.    
         [0045]    A thermal fuse, a PTC (Positive Temperature Coefficient) element, or a bimetal (for instance, a bimetallic strip) may be used, for example, as the protective device  330   a.  A thermal fuse, for example, which may be cheap and thermally sensitive, may be used as the protective device  330   a  in some embodiments. 
         [0046]    The thermal fuse may be made of a tin (Sn) alloy containing tin as a main component. In order to increase thermal sensitivity, the thermal fuse may be formed of a thin film. Considering a generally acceptable range of operating temperatures and manufacturing processes, the thermal fuse may be, for example, designed to operate at a temperature between approximately 90° C. and approximately 100° C. That is, if the operating temperature is lower than 90° C., the thermal fuse may, for example, be melted in an aging process in manufacturing rechargeable batteries. On the other hand, if the operating temperature is higher than 100° C., the risk of explosion or the like due to overheating of a rechargeable battery may not be effectively prevented. 
         [0047]    In an exemplary embodiment, a tin (Sn) alloy containing 70 to 90% of tin (Sn), 5 to 10% of zinc (Zn), 1 to 4% of lead (Pb), and the remainder of other metals may be used as the thermal fuse. In another embodiment, an alloy containing 22% of tin (Sn), 28% of lead (Pb), and 50% of bismuth (Bi) may be used as the thermal fuse. 
         [0048]    The thermal fuse may be formed of a thin film. Since the thermal fuse is formed on the bottom surface  303  of the cap plate  310   a,  it may be damaged when it reacts with an electrolyte. To avoid this, a protective film made of polyethylene or polyurethane is preferably formed with such a thermal fuse. 
         [0049]    In the foregoing disclosure, the electrode terminal  320  of the cap plate  310   a  is formed as a negative electrode terminal and the protective device  330   a  is connected between the negative electrode terminal and the negative electrode tab  140 . In other embodiments, the electrode terminal  320  of the cap plate  310   a  may be formed as a positive electrode terminal and the protective device  330   a  may be connected between the positive electrode terminal and the positive electrode tab  150 . 
         [0050]    A rechargeable battery according to another embodiment of the present invention will now be described. 
         [0051]      FIG. 4  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell  100   b  of a rechargeable battery according to another embodiment of the present invention, the bare cell  100   b  of  FIG. 4  corresponding to a portion shown for the bare cell  100  in  FIG. 3 . 
         [0052]    The rechargeable battery shown in  FIG. 4  is substantially the same as that shown in  FIG. 3  in view of configuration and functions, except that a heat blocking plate  317  is further provided in the rechargeable battery according to the embodiment shown in  FIG. 4 . Thus, a detailed explanation of similar elements or functions will not be repeated, and the illustrated embodiment of  FIG. 4  will be discussed primarily with regard to the heat blocking plate  317  in the following description. 
         [0053]    Referring to  FIG. 4 , the heat blocking plate  317  is formed between an insulation plate  313  and a protective device  330   b  using, for example, a polyurethane-based adhesive resin. The heat blocking plate  317  made of such a polyurethane-based adhesive resin can reinforce a tensile strength of the protective device  330   b  while preventing a thermal fuse from malfunctioning when an external temperature of the battery is transferred to a thermal fuse used as the protective device  330   b.    
         [0054]    A similar idea can also be applied to the bare cell  100  of  FIG. 3 . That is, the insulation plate  313  for fixing the protective device  330   a  may be made of a polyurethane resin, instead of a PP tape, thereby performing both an insulating function and a heat blocking function using only the insulation plate  313 . 
         [0055]    A rechargeable battery according to yet another embodiment of the present invention will now be described. 
         [0056]      FIG. 5  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell  100   c  of a rechargeable battery according to yet another embodiment of the present invention. 
         [0057]    The rechargeable battery shown in  FIG. 5  is substantially the same as that shown in  FIG. 3  in view of configuration and functions, except that a formation location of a protective device  330   c  is different from that of the protective device  330   a  of the embodiment shown in  FIG. 3 . In addition, a second insulation plate  313   c  and a second terminal plate  314   c  are further provided in the rechargeable battery according to the embodiment shown in  FIG. 5 . Thus, a detailed explanation of similar elements or functions will not be repeated, and in the following description, the illustrated embodiment will be discussed primarily with regard to the differences between the two embodiments. 
         [0058]    Referring to  FIG. 5 , the protective device  330   c  may be provided between (or electrically connected to) a positive electrode tab  150  and a cap plate  310   a.  That is, the second insulation plate  313   c  is formed at a location biased to the other side  302  of the cap plate  310   a  with respect to the center of a bottom surface  303  of the cap plate  310   a.  The second terminal plate  314   c  is formed between the second insulation plate  313   c  and the positive electrode tab  150 . 
         [0059]    In addition, the positive electrode tab  150  is connected to the second terminal plate  314   c,  and the protective device  330   c  is connected to the cap plate  310   a  by a fourth connection tab  319  formed at one side of the protective device  330   c.  Further, the second terminal plate  314   c  is connected to a third connection tab  318  formed at an other side of the protective device  330   c.  Thus, a current flows from the positive electrode tab  150  to the cap plate  310   a  through the protective device  330   c  without flowing directly. In addition, in other embodiments, the electrode terminal  320  of the cap plate  310   a  may serve as a positive electrode terminal, and the protective device  330   c  may be provided between the negative electrode tab  140  and the cap plate  310   a.    
         [0060]    A rechargeable battery according to still another embodiment of the present invention will now be described. 
         [0061]      FIG. 6  is a sectional view taken along the line X-X′ of  FIG. 1 , partially illustrating a bare cell  100   d  of a rechargeable battery according to still another embodiment of the present invention, the bare cell  100   d  of  FIG. 6  corresponding to a portion of the bare cell  100  shown in  FIG. 3 . 
         [0062]    The rechargeable battery shown in  FIG. 6  is substantially the same as that shown in  FIG. 3  in view of configuration and functions, except that a protective device  330   d  is integrally formed with a terminal plate (see, for example, the terminal plate  314  in  FIG. 3 ), thereby producing a combined terminal plate/protective device  330   d  in  FIG. 6 . Thus, a detailed explanation of similar elements or functions between the two embodiments will not be repeated, and in the following description, the illustrated embodiment will be discussed primarily with regard to the protective device  330   d  integrally formed with a terminal plate. 
         [0063]    Referring to  FIG. 6 , unlike in  FIG. 3  (in which the terminal plate  314  and the protective device  330   a  are separately formed on the bottom surface  303  of the insulation plate  313 ), an electrode terminal  320  and a negative electrode tab  140  are electrically connected using a protective device  330   d,  instead of also using a terminal plate (see, for example, the terminal plate  314  of  FIG. 3 ) to connect the electrode terminal  320  and the negative electrode tab  140  to each other. Thus, a separate terminal plate is not necessary, thereby simplifying a cap assembly. In addition, the electrode terminal  320  may serve as a positive electrode plate, rather than as a negative electrode plate. 
         [0064]    Although the present invention has been described with reference to the certain exemplary embodiments, the foregoing disclosure should be interpreted as illustrative only and it should be understood that various modifications and variations can be easily made by those skilled in the art without departing from the spirit or scope of the invention as defined in the following claims, and equivalents thereof.