Abstract:
A secondary battery includes an electrode assembly; a case housing the electrode assembly; a terminal electrically coupled to the electrode assembly, wherein the terminal includes a coupling part electrically coupled to the electrode assembly; and an extension part integral as a single piece with and extending from the coupling part; and a cap assembly sealing the case and comprising a cap plate and a short circuit plate, wherein the extension part at least partially covers the short circuit plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/444,545, filed on Feb. 18, 2011, in the United States Patent and Trademark Office, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the present invention relate to a secondary battery. 
     2. Description of the Related Art 
     Secondary batteries are rechargeable, unlike primary batteries which are not. Types of secondary batteries include a low capacity battery having a battery cell in the form of a pack may be used in portable small electronic devices such as cellular phones and camcorders, and a high capacity battery including tens of battery cells connected to one another may be used as a power source for driving a motor, e.g., of electric scooters, hybrid vehicles, or electric vehicles. 
     The secondary batteries are manufactured in various shapes such as a cylindrical shape and a prismatic shape. An electrolyte and an electrode assembly formed by inserting a separator as an insulator between a positive electrode plate and a negative electrode plate are accommodated in a case, and a cap plate is installed on the case to form a secondary battery. The electrode assembly is connected with a positive terminal and a negative terminal which protrude through the cap plate and are exposed to the outside of the electrode assembly. 
     SUMMARY 
     An aspect of the present invention provides a secondary battery including a smaller number of parts, thereby reducing manufacturing costs, simplifying a manufacturing process, and improving the yields thereof. 
     Further, an aspect of the present invention provides a secondary battery which can prevent a short circuit due to external moisture and a corrosion of inner parts due to external moisture. 
     In one embodiment, a secondary battery includes an electrode assembly; a case housing the electrode assembly; a terminal electrically coupled to the electrode assembly, wherein the terminal includes a coupling part electrically coupled to the electrode assembly; and an extension part integral as a single piece with and extending from the coupling part; and a cap assembly sealing the case and comprising a cap plate and a short circuit plate, wherein the extension part at least partially covers the short circuit plate. 
     In one embodiment, the secondary battery also includes a collecting plate electrically coupled to the electrode assembly and a collecting terminal electrically coupled to the collecting plate and to the coupling part, wherein the collecting terminal may penetrate through the cap plate and through the coupling part. 
     Additionally, in one embodiment, the short circuit plate may have a reversible concave portion. The extension part has an opening aligned with the concave portion of the short circuit plate. Further, in one embodiment, the cap plate has a short circuit hole, and wherein a diameter of the opening of the extension part is smaller than a diameter of the short circuit hole. Additionally, the concave portion of the short circuit plate is configured to contact the extension part when the pressure within the battery reaches a threshold level. 
     In one embodiment, the secondary battery may also include a first insulating member between the cap plate and both the coupling part and the extension part, and the first insulating member may cover the extension part. In one embodiment, the first insulating member has a first protrusion, wherein the coupling terminal has an anti-rotation recess, and wherein the first protrusion is within the anti-rotation recess. Additionally, the first insulating member may include a second protrusion, wherein the cap plate has an anti-rotation recess, and wherein the second protrusion is within the anti-rotation recess. 
     In one embodiment, the cap plate has a sealing receiver recess extending around a periphery of the first insulating member. Additionally, the secondary battery may include a second insulation member between the cap plate and the electrode assembly and the second insulation member may include a protrusion, wherein the cap plate comprises a recess, and wherein the protrusion is within the recess. Further, in one embodiment, the first insulating member includes a bottom surface, a first side wall extending from the bottom surface, and a cover extending from the first side wall which provide a space configured to accommodate the extension part. Additionally, the first insulating member includes a second side wall, wherein a height of the first side wall is greater than a height of the second side wall. The cap plate may also includes a sealing receiver recess and wherein a portion of the first insulation member is within the sealing receiver recess. Additionally, the first insulating member may have an opening aligned with the concave portion of the short circuit plate. 
     Since the first coupling terminal includes the first coupling part and the first extension part which are integrally formed, the secondary battery of embodiments of the present invention does not require a separate part that contacts the short circuit plate when the inner pressure of the secondary battery is greater than a set pressure. Thus, the number of parts constituting the secondary battery according to the embodiment is minimized, thereby reducing the manufacturing cost, simplifying a manufacturing process, and improving the yields thereof. 
     In addition, since the secondary battery according to embodiments of the present invention includes the cap plate including the sealing receiver recess, and the upper insulation member including the first side wall and the second side wall, the sealing efficiency for sealing the space between the cap plate and the upper insulation member can be improved. Thus, the secondary battery according to the embodiment can prevent external moisture from forming a short circuit between the short circuit plate and the first extension part, and prevent corrosion of inner parts due to external moisture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a secondary battery according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 ; 
         FIG. 3  is an enlarged view illustrating a portion A of  FIG. 2 ; 
         FIG. 4  is a perspective view illustrating a cap plate, a first coupling terminal, and an upper insulation member of  FIG. 3  assembled together; 
         FIG. 5  is an exploded perspective view illustrating the cap plate, the first coupling terminal, and the upper insulation member of  FIG. 4 ; 
         FIG. 6  is a cross-sectional view illustrating a part of a secondary battery according to another embodiment of the present invention; 
         FIG. 7  is a perspective view illustrating a state where a cap plate, a first coupling terminal, and an upper insulating member of  FIG. 6 . are assembled; and 
         FIG. 8  is an exploded perspective view illustrating the cap plate, the first coupling terminal, and the upper insulation member of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings. 
       FIG. 1  is a perspective view illustrating a secondary battery according to an embodiment.  FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 .  FIG. 3  is an enlarged view illustrating a portion A of  FIG. 2 .  FIG. 4  is a perspective view illustrating an assembly of a cap plate, a first coupling terminal, and an upper insulation member of  FIG. 3 .  FIG. 5  is an exploded perspective view illustrating the cap plate, the first coupling terminal, and the upper insulation member as illustrated in  FIG. 4 . 
     Referring to  FIGS. 1 through 5 , a secondary battery  100  according to an embodiment includes an electrode assembly  110 , a first terminal  120 , a second terminal  130 , a case  140 , and a cap assembly  150 . 
     The electrode assembly  110  is formed by winding or stacking a first electrode plate  111 , a separator  113 , and a second electrode plate  112 , which have a thin plate or film shape. The first electrode plate  111  may function as a negative electrode and the second electrode plate  112  may function as a positive electrode. Alternatively, the first electrode plate  111  may function as a positive electrode and the second electrode plate  112  may function as a negative electrode. 
     The first electrode plate  111  is formed by applying a first electrode active material such as graphite or carbon on a first electrode collector formed of metal foil such as nickel or copper foil, and includes a first electrode non-coating portion  111   a  on which the first electrode active metal is not applied. The first electrode non-coating portion  111   a  functions as a passage for a current flowing between the first electrode plate  111  and the outside of the first electrode plate  111 . The material of the first electrode plate  111  is not limited in the present invention. 
     The second electrode plate  112  is formed by applying a second electrode active material such as a transition metal oxide on a second electrode collector formed of metal foil such as aluminum foil, and includes a second electrode non-coating portion  112   a  on which the second electrode active metal is not applied. The second electrode non-coating portion  112   a  functions as a passage for a current flowing between the second electrode plate  112  and the outside of the second electrode plate  112 . The material of the second electrode plate  112  is not limited in the present invention. The polarities of the first and second electrode plates  111  and  112  may be reversed. 
     The separator  113  is located between the first electrode plate  111  and the second electrode plate  112  to prevent a short circuit and allow the movement of lithium ions, and may be formed of polyethylene, polypropylene, or a combined film of polypropylene and polyethylene. However, the material of the separator  113  is not limited to those listed. 
     The electrode assembly  110  and electrolyte are housed in the case  140 . The electrolyte may include an organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC), and a lithium salt such as LiPF 6  or LiBF 4 . The electrolyte may be liquid, solid, or gel. 
     Both ends of the electrode assembly  110  are coupled with first and second electrode terminals  120  and  130  that are electrically connected respectively to the first and second electrode plates  111  and  112 . 
     The first terminal  120  may be formed of a metal or an equivalent thereof, and is electrically connected to the first electrode plate  111 . The first terminal  120  may include a first collecting plate  121 , a first collecting terminal  122 , and a first coupling terminal  123 . 
     The first collecting plate  121  contacts the first electrode non-coating portion  111   a  protruding from an end of the electrode assembly  110 . Substantially, the first collecting plate  121  is welded to the first electrode non-coating portion  111   a . The first collecting plate  121  has an approximately “           ” or upside down “L” shape, and a terminal hole  121   a  is formed in the upper portion thereof. The first collecting terminal  122  is fitted into the first terminal hole  121   a . For example, the first collecting plate  121  may be formed of copper, a copper alloy, or an equivalent thereof. However, the material of the first collecting plate  121  is not limited thereto.
     The first collecting terminal  122  passes through the cap plate  151 , protrudes therefrom, and is electrically connected to the first collecting plate  121  at the lower side of the cap plate  151 . For example, the first collecting terminal  122  may be formed of one of copper, copper alloy, or an equivalent thereof. However, the material of the first collecting terminal  122  is not limited thereto. In detail, the first connecting terminal  122  includes a first body  122   a , a first flange  122   b , and a first fixing part  122   c.    
     The first body  122   a  includes an upper column protruding to the upper side of the cap plate  151 , and a lower column connected to the lower portion of the upper column and extending to the lower side of the cap plate  151 . The first body  122   a  may have a cylindrical shape, but the present invention is not limited thereto. 
     The first flange  122   b  extends horizontally from a side part of the lower column of the first body  122   a  and prevents the first collecting terminal  122  from being removed from the cap plate  151 . A portion of the lower column of the first body  122   a,  which is connected to the lower portion of the first flange  122   b , is fitted and welded to the first terminal hole  121   a  of the first collection plate  121 . 
     The first fixing part  122   c  protrudes laterally from an end of the upper column constituting the first collecting terminal  122  and fixes the first collecting terminal  122  to the first coupling terminal  123 . The first fixing part  122   c  may be formed by riveting the end of the upper column of the first collecting terminal  122 . 
     The first coupling terminal  123  is spaced from the upper side of the cap plate  151 , and more particularly is coupled to an upper insulation member (or a first insulating member)  157  located on the upper surface of the cap plate  151 . The upper column of the first collecting terminal  122  passes through and is coupled to the first coupling terminal  123  that generally corresponds to a short circuit plate  156  installed in the cap plate  151 . The first coupling terminal  123  includes a first coupling part  124  and a first extension part  125 , wherein, in one embodiment, the first coupling part  124  is integrally formed as a single piece with the first extension part  125 . In other words, the first coupling terminal  123  is made from a single piece of material and includes the first coupling part  124  and the first extension part  125 . It will be appreciated that the first coupling terminal  123  could also be made from separate materials and attached together. 
     The first coupling terminal  123  is coupled to the first collecting terminal  122  through the first coupling part  124  and is electrically insulated from the cap plate  151  through the upper insulation member  157 . The first extension part  125  of the first coupling terminal  123  may form a short circuit with the short circuit plate  156  when the short circuit plate is “activated” or reversed and protrudes upward when the inner pressure of the secondary battery  100  is greater than a set pressure. When the short circuit is formed, a large current flows through the secondary battery  100  to generate heat. As such, a fuse part formed on the first collection plate  121  or a second collection plate  131  is melted to cut off a current, thereby ensuring the safety of the secondary battery  100 . For example, the first coupling terminal  123  may be formed of one of copper, copper alloy, aluminum, aluminum alloy, or an equivalent thereof. 
     The first coupling part  124  has an approximately tetragonal column shape, and includes a first coupling body  124   a , a first collecting terminal hole  124   b , a first fixing recess  124   c , first rotation prevention recesses (or first anti-rotation recesses)  124   d , and first coupling protrusions  124   e.    
     The first coupling body  124   a  contacts the upper insulation member  157  and functions as a base to stably place the first coupling part  124  on the upper insulation member  157 . 
     The first collecting terminal hole  124   b  extends from the upper surface of the first coupling body  124   a  to the lower surface thereof and provides a space through which the upper column of the first collecting terminal  122  passes. 
     The first fixing recess  124   c  is located in the upper end of the first coupling body  124   a , has a diameter larger than the first collecting terminal hole  124   b  and provides a space for accommodating the first fixing part  122   c.    
     The first rotation prevention recesses  124   d  are formed in the lower surface of the first coupling body  124   a  and are coupled to first protrusions  157   f  located on the upper insulation member  157 . The first rotation prevention recesses  124   d  substantially prevent the rotation of the first coupling terminal  123  when the first collecting terminal  122  is coupled to the first coupling terminal  123 . 
     The first coupling protrusions  124   e  are located on both sides on the upper portion of the first coupling body  124   a , can facilitate the handling of the first coupling terminal  123 , and may provide a space for coupling a structure to the first coupling terminal  123 . 
     The first extension part  125  extends laterally from a lower edge of the first coupling body  124   a  to cover the short circuit plate  156 . The first extension part  125  may have a hole (or an opening)  125   a  located in a region generally corresponding to (i.e., generally aligned with) the short circuit plate  156 . When the short circuit plate  156  is reversed so that it protrudes away from the electrode assembly  110 , the short circuit plate  156  contacts the edge of the hole  125   a . The contact with the edge of the hole  125   a  increases a contact area between the short circuit plate  156  and the first extension part  125 . Thus, when the inner pressure of the secondary battery  100  is larger than a set pressure, a short circuit can occur more quickly between the short circuit plate  156  and the first extension part  125 . 
     Since the first coupling terminal  123  includes the first coupling part  124  and the first extension part  125  which are integrally formed, the number of parts constituting the secondary battery  100  is fewer than when a second battery includes a separate short circuit member between a collecting terminal and a coupling member to contact a reversed plate when the inner pressure of a secondary battery is greater than a set pressure. Thus, the first coupling terminal  123  makes it possible to simplify the manufacturing process for the secondary battery  100 . 
     The second terminal  130  is formed of a metal or an equivalent thereof like the first terminal  120 , and the second terminal  130  is connected to the second electrode plate  112 . The second terminal  130  may include a second collecting plate  131 , a second collecting terminal  132 , and a second coupling terminal  133 . 
     The second collecting plate  131  contacts the second electrode non-coating portion  112   a  protruding from another end of the electrode assembly  110 . Substantially, the second collecting plate  131  is welded to the second electrode non-coating portion  112   a . The second collecting plate  131  has an approximately “           ” or upside down “L” shape, and a second terminal hole  131   a  is formed in the upper portion thereof. The second collecting terminal  132  is fitted and coupled to the second terminal hole  131   a . For example, the second collecting plate  131  may be formed of one of aluminum, aluminum alloy, and an equivalent thereof. However, the material of the second collecting plate  131  is not limited thereto.
     The second collecting terminal  132  passes through the cap plate  151 , protrudes therefrom, and is electrically connected to the second collecting plate  131  at the lower side of the cap plate  151 . For example, the second collecting terminal  132  may be formed of aluminum, an aluminum alloy, or an equivalent thereof. However, the material of the second collecting terminal  132  is not limited thereto. Since the second collecting terminal  132  is generally symmetrical to the first collecting terminal  122  with respect to the center of the cap plate  151 , a description thereof will be omitted. 
     The second coupling terminal  133  is located on the upper portion of the cap plate  151 . The upper column of the second collecting terminal  132  passes through and is coupled to the second coupling terminal  133  that has an approximately tetragonal column shape. The second coupling terminal  133  may be electrically and mechanically connected to the second collecting terminal  132 . The second coupling terminal  133  may be formed of stainless steel, copper, a copper alloy, aluminum, an aluminum alloy, and an equivalent thereof, but the present invention is not limited thereto. Since the second coupling terminal  133  is symmetrical to the first coupling part  124  of the first coupling terminal  123  except for the first extension part  125  with respect to the center of the cap plate  151 , a description thereof will be omitted. 
     The case  140  is formed of a conductive metal such as aluminum, an aluminum alloy, or steel plated with nickel, and has an approximately hexahedron shape provided with an opening through which the electrode assembly  110 , the first terminal  120 , and the second terminal  130  are inserted and placed. Although the opening is not shown in  FIG. 2  since an assembly of the case  140  and the cap assembly  150  is illustrated in  FIG. 2 , a periphery of the cap assembly  150  substantially forms the opening. The inner surface of the case  140  is treated to be electrically insulated from the electrode assembly  110 , the first and second terminals  120  and  130 , and the cap assembly  150 . 
     The cap assembly  150  is coupled to the case  140 . In detail, the cap assembly  150  includes the cap plate  151 , a sealing gasket  152 , a plug  153 , a safety vent  154 , a connection plate  155 , the short circuit plate  156 , the upper insulation member  157 , and a lower insulation member (or a second insulation member)  158 . 
     The cap plate  151  seals the case  140 , and may be formed of the same material as the case  140 . The cap plate  151  may have an electrolyte injection hole  151   a , a vent hole  151   b , a short circuit hole  151   c , and a collecting terminal hole  151   d.  Here, a diameter of the hole  125   a  of the extension part  125  is smaller than a diameter of the short circuit hole  151   c . The cap plate  151  may have rotation prevention recesses (or ant-rotation recesses)  151   e  in the upper surface thereof, and coupling recesses (or recesses)  151   f  in the lower surface thereof. The cap plate  151  may be coupled to the case  140  through laser welding. Since the cap plate  151  may have the same polarity as the first electrode plate  111  and the first terminal  120 , the cap plate  151  and the case  140  may have the same polarity. 
     The seal gasket  152  is formed of an electrically insulated material and is located between the first collecting terminal  122  and the cap plate  151  to seal the space between the first collecting terminal  122  and the cap plate  151 . The seal gasket  152  substantially prevents the entry of moisture into the secondary battery  100  or the leakage of the electrolyte from the secondary battery  100 . 
     The plug  153  closes the electrolyte injection hole  151   a  of the cap plate  151 , and the safety vent  154  is installed in the vent hole  151   b  of the cap plate  151  and has a notch  154   a  openable at a set pressure. 
     The connection plate  155  is located in the cap plate  151  in a portion through which the second collecting terminal  132  passes. The connection plate  155  electrically connects the second collecting terminal  132  to the cap plate  151  and substantially prevents the entry of moisture into the secondary battery  100  or the leakage of the electrolyte from the secondary battery  100 . 
     The short circuit plate  156  is installed in the short circuit hole  151   c  of the cap plate  151 . The short circuit plate  156  may be a reversible plate that includes a round part (or a concave portion) and an edge part. The round part is formed to be convex downward (i.e., towards the electrode assembly  110 ) and the edge part is fixed to the cap plate  151 . When the interior pressure of the secondary battery  100  becomes greater than a set pressure, the short circuit plate  156  is reversed and protrudes upward (i.e., away from the electrode assembly) and contacts the first extension part  125  of the first coupling terminal  123  to form a short circuit. The short circuit plate  156  has the same polarity as the cap plate  151 . 
     The upper insulation member  157  is located between the first coupling terminal  123  and the cap plate  151  and accommodates the first coupling terminal  123 . The upper insulation member  157  includes a bottom  157   a , a first side wall  157   b , a second side wall  157   c , and a cover  157   d . Further, the upper insulation member  157  includes a terminal through hole  157   e , first protrusions  157   f , second protrusions  157   g,  and an opening  157   h.    
     The bottom  157   a  contacts the cap plate  151  and functions as a base for stably placing the upper insulation member  157  on the cap plate  151 . 
     The first side wall  157   b  extends from edges of the bottom  157   a , and substantially provides a space to accommodate the first coupling terminal  123  in the upper insulation member  157 . In one embodiment, the first side wall  157   b  does not extend around an entire periphery of the bottom  157   a , but rather only extends around three sides of the bottom  157   a . The first side wall  157   b  has a height H 1 . 
     The second side wall  157   c  extends upward from an edge of the bottom  157   a  in a region that does not include the first side wall  157   b  and has a height H 2  smaller than the height H 1  of the first side wall  157   b . The second side wall  157   c  facilitates insertion of the first extension part  125  of the first coupling terminal  123  to the upper insulation member  157 . 
     The cover  157   d  is connected to a portion of the edge of the first side wall  157   b  to cover the first extension part  125  of the first coupling terminal  123  accommodated in the upper insulation member  157 . The cover  157   d  is located at a position corresponding to the first extension part  125  of the first coupling terminal  123 , wherein a portion corresponding the first coupling part  124  of the first coupling terminal  123  in the upper insulation member  157  is opened or exposed. The cover  157   d  may be parallel to the bottom  157   a  and is sized to generally correspond to the first extension part  125  of the first coupling terminal  123 . 
     The terminal through hole  157   e  is located in the bottom  157   a  facing the cover  157   d  to accommodate the first collecting terminal  122 . 
     The first protrusions  157   f  are located in the upper surface of the bottom  157   a  in regions adjacent to the terminal through hole  157   e  and are coupled to the first rotation prevention recesses  124   d.    
     The second protrusions  157   g  are located in the lower surface of the bottom  157   a  in regions adjacent to the terminal through hole  157   e  and are coupled to the rotation prevention recesses  151   e . The opening  157   h  is aligned with the round part of the short circuit plate  156 . 
     The lower insulation member  158  is located between the cap plate  151  and each of the first and second collecting plates  121  and  131  to prevent an unnecessary short circuit. In other words, the lower insulation members  158  prevent a short circuit between the cap plate  151  and the first collecting plate  121 , and a short circuit between the cap plate  151  and the second collecting plate  131 . The lower insulation member  155  is also located between the cap plate  151  and each of the first and second collecting terminals  122  and  132  to prevent an unnecessary short circuit between the cap plate  151  and each of the first and second collecting terminals  122  and  132 . The lower insulation member  158  may include protrusions  158   a  that are formed on the upper surface thereof and are coupled to the coupling recesses  151   f  of the cap plate  151 . 
     Since the first coupling terminal  123  includes the first coupling part  124  and the first extension part  125  which are integrally formed as a single piece, the secondary battery  100  does not require a separate part that contacts the short circuit plate  156  when the inner pressure of the secondary battery  100  becomes greater than a set pressure. 
     Thus, the number of parts constituting the secondary battery according to the embodiment is minimized, thereby reducing the manufacturing cost, simplifying a manufacturing process, and improving the yields thereof. 
       FIG. 6  is a cross-sectional view illustrating a part of a secondary battery according to another embodiment.  FIG. 7  is a perspective view illustrating an assembled cap plate, first coupling terminal, and upper insulating member of  FIG. 6 .  FIG. 8  is an exploded perspective view illustrating the cap plate, the first coupling terminal, and the upper insulation member as illustrated in  FIG. 7 . 
     A secondary battery according to an embodiment has generally the same configuration as the secondary battery  100  of  FIG. 2  except for a cap plate  251  and an upper insulation member  257 . Thus, an illustration and a description of the same configuration will be omitted, and the cap plate  251  and the upper insulation member  257  will be primarily described. 
     The cap plate  251  is similar to the cap plate  151 . However, the cap plate  251  includes a sealing receiver recess  251   a  in the upper surface thereof. A first side wall  257   b  of the upper insulation member  257  and a second side wall  257   c  thereof are partially fitted into the sealing receiver recess  251   a . The sealing receiver recess  251   a  improves physical coupling force of the cap plate  251  and the upper insulation member  257 , and sealing efficiency for sealing the space between the cap plate  251  and the upper insulation member  257 . Thus, external moisture between the cap plate  251  and the upper insulation member  257  can be prevented from creating a short circuit between the short circuit plate  156  and the first extension part  125 , and corrosion of internal components due to external moisture can be significantly prevented. 
     The upper insulation member  257  is similar to the upper insulation member  157 . However, the first and second side walls  257   b  and  257   c  of the upper insulation member  257  further extend downward toward the electrode assembly from the bottom  157   a . Thus, the first and second side walls  257   b  and  257   c  extending downward from the bottom  157   a  can be partially accommodated in the sealing receiver recess  251   a  of the cap plate  251 . 
     As described above, since the secondary battery according to the current embodiment includes the cap plate  251  including the sealing receiver recess  251   a , and the upper insulation member  257  including the first side wall  257   b  and the second side wall  257   c , sealing efficiency for sealing the space between the cap plate  251  and the upper insulation member  257  can be improved. 
     Thus, the secondary battery according to the current embodiment can prevent external moisture from creating a short circuit between the short circuit plate  156  and the first extension part  125 , and prevent corrosion of inner parts. 
     Although the present invention has been described with reference to the preferred examples, the foregoing disclosure should be interpreted as illustrative only and it should be understood that various modifications and equivalent embodiments can be easily made by those skilled in the art without departing from the spirit of the invention. Accordingly, the true scope and spirit of the invention should be defined by the following claims. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 DESCRIPTION OF THE SYMBOLS IN MAIN 
               
               
                 PORTIONS OF THE DRAWINGS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 100: Secondary battery 
                 110: Electrode assembly 
               
               
                 120: First terminal 
                 121: First collecting plate 
               
               
                 122: First collecting terminal 
                 123: First coupling terminal 
               
               
                 124: First coupling part 
                 125: First extension part 
               
               
                 130: Second terminal 
                 131: Second collecting plate 
               
               
                 132: Second collecting terminal 
                 133: Second coupling terminal 
               
               
                 140: Case 
                 150: Cap assembly 
               
               
                 151, 251: Cap plate 
                 152: Sealing gasket 
               
               
                 153: Plug 
                 154: Safety vent 
               
               
                 155: Connection plate 
                 156: Short circuit plate 
               
               
                 157, 257: Upper insulation member 
                 158: Lower insulation member 
               
               
                 251a: Sealing receiver recess