Abstract:
A rechargeable battery includes an electrode assembly; a case housing the electrode assembly; a cap assembly comprising a cap plate that seals the case and has an opening; and a short circuit member including a first short circuit plate extending across the opening, a second short circuit plate spaced from the cap plate and covering the opening, and a third short circuit plate between the first and second short circuit plates.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0007047, filed Jan. 26, 2010, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments relate to a rechargeable battery. 
         [0004]    2. Description of the Related Art 
         [0005]    Unlike a primary battery that is not rechargeable, a rechargeable battery is dischargeable and rechargeable. A low capacity battery having a battery cell packaged in the form of a pack is generally used for small, portable electronic devices such as a mobile phone or a camcorder. A large capacity battery having tens of battery packs interconnected is widely used as a power source for driving a motor of a hybrid vehicle and the like. 
         [0006]    The rechargeable battery is formed in a variety of shapes such as a prismatic shape, a cylinder shape, and the like. The rechargeable battery typically includes an electrode assembly having positive and negative electrode plates and a separator between the positive and negative electrode plate, a case receiving the electrode assembly as well as electrolyte, and a cap assembly having electrode terminals and installed on the case. 
         [0007]    Overcharging may excessively heat a rechargeable battery, or decomposition of electrolyte may increase an inner pressure of the rechargeable battery to cause a spark or explosion. Thus, a rechargeable battery having a structure for improving stability is desired. 
       SUMMARY 
       [0008]    An aspect of the present invention provides a rechargeable battery that prevents or reduces the likelihood of melting due to contact between short circuit plates and that maintains a short circuit state caused by the contact so that a fuse part can continually function as a fuse. 
         [0009]    According to at least one of the embodiments, a rechargeable battery includes an electrode assembly; a case housing the electrode assembly; a cap assembly comprising a cap plate that seals the case and has a short circuit opening; and a short circuit member comprising a first short circuit plate extending across the short circuit opening, a second short circuit plate spaced from the cap plate and covering the short circuit opening, and a third short circuit plate between the first and second short circuit plates. 
         [0010]    In one embodiment, the third short circuit plate is spaced from the second short circuit plate and more specifically, a first end of the third short circuit plate is coupled to the cap plate adjacent the short circuit opening, and a second end of the third short circuit plate is spaced from the cap plate. Further, in one embodiment, the third short circuit plate is configured to contact the second short circuit plate by movement of the first short circuit plate when an inner pressure of the rechargeable battery is greater than a set pressure. 
         [0011]    In one embodiment, the first short circuit plate comprises a reversible plate that has a convex part protruding toward the electrode assembly and an edge part fixed to the cap plate. Additionally, a surface of the cap plate defining the short circuit opening may be stepped, and a diameter of the short circuit opening may increase in a direction away from the electrode assembly. In one embodiment, the surface of the cap plate has a first step, a second step and a third step in order in a direction away from the electrode assembly, wherein the first short circuit plate is fixed to the first step, and wherein the third short circuit plate is fixed to the second step. 
         [0012]    In one embodiment, the rechargeable battery may also include an upper insulating member located between the second short circuit plate and the cap plate, wherein the upper insulating member has an opening generally corresponding to the short circuit opening. Further, the second short circuit plate may have a flat surface facing the third short circuit plate, and the third short circuit plate may have a chamfer adapted to contact the second short circuit plate. 
         [0013]    Additionally, in one embodiment, the second short circuit plate includes an opening; and a protrusion extending towards the third short circuit plate and protruding from a periphery of the opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain principles of the present disclosure. In the drawings: 
           [0015]      FIG. 1  is a perspective view illustrating a rechargeable battery according to an embodiment; 
           [0016]      FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 ; 
           [0017]      FIG. 3A  is a detailed cross-sectional view illustrating portion A of  FIG. 2 ; 
           [0018]      FIG. 3B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 3A  contacts a second short circuit plate of  FIG. 3A ; 
           [0019]      FIG. 4A  is a detailed cross-sectional view illustrating a portion generally corresponding to the portion A of  FIG. 2  in a rechargeable battery according to another embodiment; 
           [0020]      FIG. 4B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 4A  contacts a second short circuit plate of  FIG. 4A ; 
           [0021]      FIG. 5A  is an enlarged cross-sectional view illustrating a portion corresponding to the portion A of  FIG. 2  in a rechargeable battery according to another embodiment; 
           [0022]      FIG. 5B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 5A  contacts a second short circuit plate of  FIG. 5A ; 
           [0023]      FIG. 6A  is an enlarged cross-sectional view illustrating a portion corresponding to the portion A of  FIG. 2  in a rechargeable battery according to another embodiment; and 
           [0024]      FIG. 6B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 6A  contacts a second short circuit plate of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. 
         [0026]    Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.  FIG. 1  is a perspective view illustrating a rechargeable battery according to an embodiment.  FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 .  FIG. 3A  is an enlarged cross-sectional view illustrating a portion A of  FIG. 2 .  FIG. 3B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 3A  contacts a second short circuit plate of  FIG. 3A . 
         [0027]    Referring to  FIGS. 1 and 2 , a rechargeable battery  100  according to the current embodiment includes an electrode assembly  10 , a first collecting plate  20 , a second collecting plate  30 , a case  40 , a cap assembly  50 , and a short circuit member  60 . 
         [0028]    The electrode assembly  10  is formed by winding or stacking a first electrode plate  11 , a separator  13 , and a second electrode plate  12 , which have thin plate shapes or film shapes. The first electrode plate  11  may function as a positive electrode, and the second electrode plate  12  may function as a negative electrode. 
         [0029]    The first electrode plate  11  is formed by applying first electrode active materials such as transition metal oxide on a first electrode collector formed of metal foil such as aluminum foil, and includes first electrode non-coating portions  11   a  on which the first electrode active materials are not applied. The first electrode non-coating portions  11   a  function as passages for current flow between the first electrode plate  11  and the outside of the first electrode plate  11 . The material of the first electrode plate  11  is not limited to those disclosed by the present disclosure. 
         [0030]    The second electrode plate  12  is formed by applying second electrode active materials such as graphite or carbon on a second electrode collector formed of metal foil such as nickel or copper foil, and includes second electrode non-coating portions  12   a  on which the second electrode active materials are not applied. The second electrode non-coating portions  12   a  function as passages through which a current flows between the second electrode plate  12  and the outside of the second electrode plate  12 . The material of the second electrode plate  12  is not limited to those disclosed by the scope of the present disclosure. 
         [0031]    The polarity of the first electrode plate  11  and the polarity of the second electrode plate  12  may be interchanged with each other. 
         [0032]    The separator  13  is located between the first electrode plate  11  and the second electrode plate  12  to prevent a short circuit and to allow lithium ions to move, and is formed as a film of one of polyethylene, polypropylene, a combination thereof. However, the material of the separator  13  is not limited to those disclosed by the present disclosure. 
         [0033]    Both ends of the electrode assembly  10  are connected with the first collecting plate  20  and the second collecting plate  30  that are respectively connected to the first electrode plate  11  and the second electrode plate  12 . 
         [0034]    The first collecting plate  20  is formed of a conductive material such as aluminum, and is in contact with the first electrode non-coating portions  11   a  protruding from one end of the electrode assembly  10 , so that the first collecting plate  20  is electrically coupled to the first electrode plate  11 . Referring to  FIG. 2 , the first collecting plate  20  may include a first connection part  21 , a first extension part  23 , a first terminal hole  24 , and a first fuse part  25 . 
         [0035]    The first connection part  21  is installed between the upper part of the electrode assembly  10  and the lower part of the cap assembly  50 , and is formed in a plate shape. 
         [0036]    The first extension part  23  is bent at angle and extends from an end of the first connection part  21 , and is formed in a plate shape that is substantially in contact with the first electrode non-coating portions  11   a . A corner where the first connection part  21  meets the first extension part  23  is denoted by ‘C’, and the first connection part  21  may be substantially perpendicular to the first extension part  23  at the corner C. 
         [0037]    The first terminal hole  24  is located at a side of the first connection part  21 , and provides the first connection part  21  with a space into which a first electrode terminal  52  of the cap assembly  50  is fitted and coupled. The first terminal hole  24  is at a portion of the first connection part  21  which is spaced from the corner C. 
         [0038]    The first fuse part  25  is located on the first connection part  21  on the upper side of the electrode assembly  10  such that the first fuse part  25  does not contact electrolyte. In addition, the first fuse part  25  is located in a region of the first connection part  21  adjacent to the corner C such that the first fuse part  25  does not overlap the first electrode terminal  52  coupled to the first terminal hole  24 . In one embodiment, the first fuse part  25  includes a first fuse hole  25   a  and a first reinforcement protrusion  25   b  protruding from a periphery of the first fuse hole  25   a . When a short circuit occurs in the rechargeable battery  100 , a large current flows in the rechargeable battery  100  and heat is generated, which may melt the region where the first fuse hole  25   a  is located to allow the first fuse hole  25   a  to function as a fuse to shut off a current flow. The first reinforcement protrusion  25   b  reinforces the region where the first fuse hole  25   a  is located against external shock during operation of the battery. 
         [0039]    The second collecting plate  30  is formed of a conductive material such as nickel, and is in contact with the second electrode non-coating portions  12   a  protruding from another end of the electrode assembly  10 , so that the second collecting plate  30  is electrically coupled to the second electrode plate  12 . The second collecting plate  30  may include a second connection part  31 , a second extension part  33 , and a second terminal hole  34 . 
         [0040]    Since the second connection part  31 , the second extension part  33 , and the second terminal hole  34  of the second collecting plate  30  are substantially the same shape and serve substantially the same function as the first connection part  21 , the first extension part  23 , and the first terminal hole  24  of the first collecting plate  20  as illustrated in  FIG. 2 , descriptions thereof will be omitted. 
         [0041]    The case  40  is formed of conductive metal such as steel plated with aluminum, aluminum alloy, or nickel, and has an approximately hexahedron shape provided with an opening part through which the electrode assembly  10 , the first collecting plate  20 , and the second collecting plate  30  can be inserted and placed. Since  FIG. 2  illustrates the case  40  coupled to the cap assembly  50 , the opening part is not shown, but the edge of the case  40  corresponding to the cap assembly  50  is substantially open. The inner surface of the case  40  is electrically insulated from the electrode assembly  10 , the first collecting plate  20 , the second collecting plate  30 , and the cap assembly  50 . In this case, the case  40  may function as a pole, e.g., a positive pole. 
         [0042]    The cap assembly  50  is coupled to the case  40 . In detail, the cap assembly  50  may include a cap plate  51 , the first electrode terminal  52 , the second electrode terminal  53 , gaskets  54 , and nuts  55 . The cap assembly  50  may further include a cap  56 , a vent plate  57 , a connection plate  58 , an upper insulating member  59   a , and lower insulating members  59   b.    
         [0043]    The cap plate  51  seals an opening of the case  40 , and may be formed of the same material as the case  40 . The cap plate  51  may include an electrolyte injection hole  51   a , a vent hole  51   b , and a short circuit opening  51   c . A side surface of the short circuit opening  51   c  may be stepped, and the diameter of the short circuit opening  51   c  may increase from the lower side to the upper side. Accordingly, the side surface of the short circuit opening  51   c  may include a first step SS 1 , a second step SS 2 , and a third step SS 3 . The cap plate  51  may have the same polarity as that of the case  40 . 
         [0044]    The first electrode terminal  52  passes through a side of the cap plate  51 , and is electrically coupled to the first collecting plate  20 . The first electrode terminal  52  may have a column shape. The outer circumferential edge of an upper portion of the column shape exposed to the upper side of the cap plate  51  is provided with a screw thread. The lower portion of the column shape at the lower side of the cap plate  51  is provided with a flange  52   a  to prevent the first electrode terminal  52  from being separated from the cap plate  51 . A portion of the column shape of the first electrode terminal  52  at the lower side of the flange  52   a  is fitted into the first terminal hole  24  of the first collecting plate  20 . The first electrode terminal  52  may be electrically coupled to the cap plate  51 . 
         [0045]    The second electrode terminal  53  passes through another side of the cap plate  51 , and is electrically coupled to the second collecting plate  30 . Since the second electrode terminal  53  has the same shape as that of the first electrode terminal  52 , a description thereof will be omitted. However, the second electrode terminal  53  is electrically insulated from the cap plate  51 . 
         [0046]    The gasket  54  is formed of an insulating material, and is located between the cap plate  51  and each of the first electrode terminal  52  and the second electrode terminal  53  to seal the space between the cap plate  51  and each of the first electrode terminal  52  and the second electrode terminal  53 . The gaskets  54  prevent moisture from entering the rechargeable battery  100  and prevent electrolyte stored in the rechargeable battery  100  from leaking to the outside. 
         [0047]    The nuts  55  are coupled along the screw threads provided respectively to the first electrode terminal  52  and the second electrode terminal  53 , to respectively fix the first electrode terminal  52  and the second electrode terminal  53  to the cap plate  51 . 
         [0048]    The cap  56  seals the electrolyte injection hole  51   a  of the cap plate  51 . The vent plate  57  is installed in the vent hole  51   b  of the cap plate  51 , and includes a notch  57   a  to be opened at a set pressure. 
         [0049]    The connection plate  58  is configured such that the first electrode terminal  52  is fitted between the first electrode terminal  52  and the cap plate  51 , and is coupled to the cap plate  51  and the gasket  54  through the nut  55 . The connection plate  58  electrically couples the first electrode terminal  52  to the cap plate  51 . 
         [0050]    The upper insulating member  59   a  configured such that the second electrode terminal  53  is fitted between the second electrode terminal  53  and the cap plate  51 , and is proximate to the cap plate  51  and the gasket  54 . The upper insulating member  59   a  insulates the second electrode terminal  53  and the cap plate  51 . 
         [0051]    The lower insulating member  59   b  is located between the cap plate  51  and each of the first collecting plate  20  and the second collecting plate  30  to prevent an unnecessary short circuit. 
         [0052]    The short circuit member  60  is installed on the upper side of the cap assembly  50 . When an inner pressure of the rechargeable battery  100  is greater than a set pressure caused by, for example, overcharging, the short circuit member  60  induces a short circuit such that the first fuse part  25  shuts off a current flow. The short circuit member  60  includes a first short circuit plate  61 , a second short circuit plate  62 , and a third short circuit plate  63 , which are formed of a conductive material. 
         [0053]    Referring to  FIG. 3A , the first short circuit plate  61  is installed in the short circuit opening  51   c  of the cap plate  51 . The first short circuit plate  61  is formed as a reversible plate that includes a convex part  61   a  protruding downward generally towards an interior of the case  40  and an edge part  61   b  fixed to the side surface of the short circuit opening  51   c , that is, to the first step SS 1 . The first short circuit plate  61  is electrically coupled to the cap plate  51 . When an inner pressure of the rechargeable battery  100  is greater than a set pressure, the first short circuit plate  61  may be reversed to be convex upward, protruding generally away from an interior of the case  40 . The first short circuit plate  61  may be formed of aluminum, but the present disclosure is not limited thereto. The first short circuit plate  61  may have a thickness between about 0.4 mm to about 0.6 mm, but the present disclosure is not limited thereto. 
         [0054]    The second short circuit plate  62  is located on an exterior of the cap plate  51  and spaced from the cap plate  51 , and the second electrode terminal  53  is fitted into the second short circuit plate  62 . The second short circuit plate  62  extends to cover the short circuit opening  51   c . The second short circuit plate  62  is electrically coupled to the second electrode terminal  53 . The second short circuit plate  62  has generally flat upper and lower surfaces, and is formed of copper, but the present disclosure is not limited thereto. The second short circuit plate  62  may have a thickness of about 1 mm or greater, but the present disclosure is not limited thereto. 
         [0055]    The third short circuit plate  63  is spaced from the second short circuit plate  62  and is located between the first short circuit plate  61  and the second short circuit plate  62 . The third short circuit plate  63  has flat upper and lower surfaces. Referring to  FIG. 3B , via the convex part  61   a  that reverses to protrude upward when the inner pressure of the rechargeable battery  100  is greater than a set pressure, the third short circuit plate  63  is brought into contact with the second short circuit plate  62  to cause a short circuit. When the short circuit occurs, a large current flows, and heat is generated, causing the first fuse part  25  to function as a fuse, thereby improving the stability of the rechargeable battery  100 . The third short circuit plate  63  may be in linear contact with the second short circuit plate  62 . 
         [0056]    In one embodiment, to contact the second short circuit plate  62 , the third short circuit plate  63  has a first side connected to a first side of the short circuit opening  51   c , and a second side spaced from a second side of the short circuit opening  51   c.    
         [0057]    That is, a first end of the third short circuit plate  63  is fixed to the second step SS 2 , and a second end of the third short circuit plate  63  is spaced from the second step surface SS 2  such that the second side of the third short circuit plate  63  is movable upward generally away from the electrode assembly. The third short circuit plate  63  may electrically coupled to the cap plate  51 , and may be formed of aluminum, but the present disclosure is not limited thereto. 
         [0058]    The third short circuit plate  63  may have a greater thickness than the first short circuit plate  61 , for example, a thickness ranging from about 0.7 mm to about 0.8 mm. Instead of the first short circuit plate  61  having a small thickness, the third short circuit plate  63  may contact the second short circuit plate  62  to cause a short circuit. Accordingly, the third short circuit plate  63  substantially prevents the first short circuit plate  61  from being melted before the first fuse part  25  functions as a fuse when the first short circuit plate  61  contacts the second short circuit plate  62  to cause a short circuit. Thus, when the rechargeable battery  100  is overcharged, and an inner pressure of the rechargeable battery  100  is greater than a set pressure, the third short circuit plate  63  maintains a short circuit so that the first fuse part  25  can function as a fuse. 
         [0059]    As described above, the rechargeable battery  100  includes the third short circuit plate  63  thicker than the first short circuit plate  61  between the first short circuit plate  61  and the second short circuit plate  62  to prevent melting of the first short circuit plate  61  due to contact between the second short circuit plate  62  and the thin first short circuit plate  61 . 
         [0060]    Thus, when an inner pressure of the rechargeable battery  100  is greater than a set pressure by a state such as overcharge, the rechargeable battery  100  maintains a short circuit caused by contact of the second short circuit plate  62  with the third short circuit plate  63 , so that the first fuse part  25  can continually function as a fuse. 
         [0061]    Hereinafter, a rechargeable battery will now be described according to another embodiment. 
         [0062]      FIG. 4A  is an enlarged cross-sectional view illustrating a portion corresponding to the portion A of  FIG. 2  in the rechargeable battery according to the current embodiment.  FIG. 4B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 4A  contacts a second short circuit plate of  FIG. 4A . 
         [0063]    The rechargeable battery according to the current embodiment is the same in configurations and functions as the rechargeable battery  100  illustrated in  FIG. 2  except for a configuration of a third short circuit plate  163  of a short circuit member  160 . Thus, illustrations and descriptions of the same configurations will be omitted, and the third short circuit plate  163  will be principally described. 
         [0064]    Referring to  FIG. 4A , the short circuit member  160  of the rechargeable battery according to the current embodiment includes the first short circuit plate  61 , the second short circuit plate  62 , and the third short circuit plate  163 , which are formed of conductive material. 
         [0065]    The third short circuit plate  163  is similar to the third short circuit plate  63  as illustrated in  FIG. 3A . However, the third short circuit plate  163  includes a chamfer  163   a  formed by cutting a side of a surface facing the second short circuit plate  62 . Referring to  FIG. 4B , when the third short circuit plate  163  is moved upward by the first short circuit plate  61 , the third short circuit plate  163  is in surface contact with the second short circuit plate  62  to reduce resistance due to the contact between the third short circuit plate  163  and the second short circuit plate  62 . 
         [0066]    As described above, the rechargeable battery according to the current embodiment includes the third short circuit plate  163  having the chamfer  163   a  to suppress the case in which the portion where the third short circuit plate  163  contacts the second short circuit plate  62  is melted by the first short circuit plate  61  that protrudes upward when the rechargeable battery  100  is overcharged and its inner pressure is greater than a set pressure. 
         [0067]    Hereinafter, a rechargeable battery will now be described according to another embodiment. 
         [0068]      FIG. 5A  is an enlarged cross-sectional view illustrating a portion corresponding to the portion A of  FIG. 2  in the rechargeable battery according to the current embodiment.  FIG. 5B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 5A  contacts a second short circuit plate of  FIG. 5A . 
         [0069]    The rechargeable battery according to the current embodiment is substantially the same in configuration and function as the rechargeable battery  100  illustrated in  FIG. 2  except for a configuration of a second short circuit plate  262  of a short circuit member  260 . Thus, illustrations and descriptions of components with the same configuration will be omitted, and the second short circuit plate  262  will be primarily described. 
         [0070]    Referring to  FIG. 5A , the short circuit member  260  of the rechargeable battery according to the current embodiment includes the first short circuit plate  61 , the second short circuit plate  262 , and the third short circuit plate  63 , which are formed of a conductive material. 
         [0071]    The second short circuit plate  262  is similar to the second short circuit plate  62  illustrated in  FIG. 3A . However, the second short circuit plate  262  includes an opening  262   a  and a protrusion  262   b.    
         [0072]    When the second short circuit plate  262  contacts the third short circuit plate  63  to form a short circuit, the opening  262   a  allows for a constant current flow. That is, since resistance is large in a contact region between the second short circuit plate  262  and the third short circuit plate  63 , the opening  262   a  minimizes the resistance variation in the contact region between the second short circuit plate  262  and the third short circuit plate  63 , with respect to the other regions. 
         [0073]    The protrusion  262   b  is located on a surface facing the third short circuit plate  63 , and protrudes from a periphery of the opening  262   a . The protrusion  262   b  reduces the distance between the second short circuit plate  262  and the third short circuit plate  63 , so that the first short circuit plate  61  can more reliably ensure that the third short circuit plate  63  sufficiently contacts the second short circuit plate  262 . 
         [0074]    As described above, the rechargeable battery according to the current embodiment includes the second short circuit plate  262  having the opening  262   a  and the protrusion  262   b  to facilitate a short circuit due to the contact between the second short circuit plate  262  and the third short circuit plate  63  by the first short circuit plate  61  that is reversed upward when the rechargeable battery  100  is overcharged and its inner pressure is greater than a set pressure. 
         [0075]    Hereinafter, a rechargeable battery will now be described according to another embodiment. 
         [0076]      FIG. 6A  is an enlarged cross-sectional view illustrating a portion corresponding to the portion A of  FIG. 2  in the rechargeable battery according to the current embodiment.  FIG. 6B  is a cross-sectional view illustrating a case in which a third short circuit plate of  FIG. 6A  contacts a second short circuit plate of  FIG. 6A . 
         [0077]    The rechargeable battery according to the current embodiment is substantially the same in configuration and function as the rechargeable battery  100  illustrated in  FIG. 2  except for the configuration of the second short circuit plate  262  and the third short circuit plate  163  of a short circuit member  360 . Thus, illustrations and descriptions of the components with the same configuration will be omitted, and the second short circuit plate  262  and the third short circuit plate  163  will be primarily described. 
         [0078]    Referring to  FIG. 6A , the short circuit member  360  of the rechargeable battery according to the current embodiment includes the first short circuit plate  61 , the second short circuit plate  262 , and the third short circuit plate  163 , which are formed of conductive material. 
         [0079]    The second short circuit plate  262  is similar to the second short circuit plate  62  illustrated in  FIG. 3A . However, the second short circuit plate  262  includes the opening  262   a  and the protrusion  262   b . Since the second short circuit plate  262  is described in  FIG. 5A , the description is omitted in the current embodiment. 
         [0080]    The third short circuit plate  163  is similar to the third short circuit plate  63  as illustrated in  FIG. 3A . However, the third short circuit plate  163  includes the chamfer  163   a  formed by cutting a side of the surface facing the second short circuit plate  262 . Since the third short circuit plate  163  is described in  FIG. 4A , the description is omitted in the current embodiment. 
         [0081]    As described above, the rechargeable battery according to the current embodiment includes the second short circuit plate  262  having the opening  262   a  and the protrusion  262   b , and the third short circuit plate  163  having the chamfer  163   a , to reduce the likelihood that when the third short circuit plate  163  contacts the second short circuit plate  262 , the third short circuit plate is melted by the first short circuit plate  61  that reverses to protrude upward when the rechargeable battery  100  is overcharged and its inner pressure is greater than a set pressure, and simultaneously, to facilitate a short circuit due to the contact between the second short circuit plate  262  and the third short circuit plate  163 . 
         [0082]    The rechargeable battery according to the current embodiments includes the third short circuit plate thicker than the first short circuit plate between the first short circuit plate and the second short circuit plate to prevent melting of the first short circuit plate when the second short circuit plate contacts the thin first short circuit plate. 
         [0083]    Accordingly, when an inner pressure of the rechargeable battery is greater than a set pressure by a state such as overcharge, the rechargeable battery maintains a short circuit state caused by contact of the second short circuit plate with the third short circuit plate, so that the fuse part can continually function as a fuse. 
         [0084]    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 disclosure as set forth in the following claims.