Abstract:
A secondary battery including: a wound electrode assembly, including, a first electrode tab and a second electrode tab; a can to house the electrode assembly and an electrolyte, having a threaded neck and an opening; and a threaded cap to seal the can by mating with the neck. The neck may have an external threaded surface, and the cap may have an internal threaded surface that mates with the threaded surface of the neck. A sealing material may applied between the neck and the cap, to adhere the same.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0124698, filed on Dec. 15, 2009, in the Korean Intellectual Property Office, which is incorporated herein, by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    An aspect of the present disclosure relates to a secondary battery. 
         [0004]    2. Description of the Related Art 
         [0005]    As the miniaturization of portable electronic devices has progressed, much research has been conducted to develop secondary batteries for such portable electronic devices. 
         [0006]    Unlike batteries that are not rechargeable, secondary batteries are rechargeable and are widely used in portable electronic devices, such as cellular phones, notebook computers and camcorders. Particularly, lithium secondary batteries have an operating voltage of 3.6 V, which is three times higher than that of nickel-cadmium batteries or nickel-hydride batteries. Lithium secondary batteries have an excellent energy density per unit weight, and therefore, the use of the lithium secondary batteries has rapidly increased. 
         [0007]    In such lithium secondary batteries, a lithium-based oxide is used as a positive electrode active material, and a carbon material is used as a negative electrode active material. Lithium secondary batteries are manufactured in various types, such as a cylindrical, prismatic, and pouch-type. 
         [0008]    A cylindrical type secondary battery includes an electrode assembly, a cylindrical type can, a cap assembly, a gasket, and the like. As disclosed in Korean Patent Laid-Open Publication No. 10-2007-0071235, and the like, a general cap assembly includes many components, such as a safety vent, a current blocking unit, a secondary protection device, and a cap-up. Therefore, manufacturing costs are increased and manufacturing efficiency is reduced. 
       SUMMARY 
       [0009]    Additional aspects and/or advantages of the present disclosure 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 present disclosure. 
         [0010]    In one exemplary embodiment, there is provided a secondary battery having a simplified structure ensuring stability. 
         [0011]    According to an aspect of the present disclosure, there is provided a secondary battery including: an electrode assembly including a first electrode, a second electrode, and a separator interposed therebetween, which are wound together; first and second electrode tabs respectively attached to the first and second electrodes; a cylindrical can accommodating the electrode assembly and an electrolyte, having an opening and a threaded neck; a threaded cap screw-connected to the neck; and a sealing material adhering the neck to the cap. 
         [0012]    According to various embodiments, the secondary battery may further include an elastic body positioned between the electrode assembly and the cap, to maintain the spacing therebetween. 
         [0013]    According to various embodiments, the elastic body may be a metal spring that surrounds the first electrode tab and/or a heat-resistance sponge that is filled in a space between the electrode assembly and the cap, having an opening through which the first electrode tab passes. The electrolyte may be absorbed in the heat-resistance sponge. 
         [0014]    According to various embodiments, the secondary battery may further include a contact plate positioned between the electrode assembly and the cap, to electrically connect the first electrode tab and the cap. The secondary battery may further include an elastic body disposed around the first electrode tab, to maintain the spacing between the electrode assembly and the contact plate. The contact plate may be welded between the first electrode tab and the cap, to electrically connect the same. 
         [0015]    According to various embodiments, the cylindrical can may have a projection that contacts the second electrode tab, to electrically connect the second electrode tab to the cylindrical can. The projection may be formed on a bottom surface of the cylindrical can. The projection and the second electrode tab may be electrically connected to each other through welding. 
         [0016]    According to various embodiments, the sealing material may be coated on the outer surface of the neck or the inner surface of the cap and then heat fused, to adhere the cap to the neck. 
         [0017]    According to various embodiments, the sealing material may include a polypropylene-based material. 
         [0018]    In a secondary battery according to an exemplary embodiment, a cylindrical can and a cap are screw-connected to each other and adhered together with a sealing material, so that it is possible to employ a simplified structure having only a small number of components and to secure the stability of the connection. 
         [0019]    According to various embodiments, when an elastic body such as a metal spring or heat-resistance sponge is provided between an electrode assembly and a cap, it is possible to stably support the electrode assembly and maintain the spacing between the electrode assembly and the cap. 
         [0020]    According to various embodiments, an electrolyte is absorbed in the heat-resistance sponge, such that the stored electrolyte can be used to replenish the electrolyte stored in the can, thereby extending the lifetime of the secondary battery. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    These and/or other aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which: 
           [0022]      FIG. 1  is an exploded perspective view of a secondary battery, according to an exemplary embodiment of the present disclosure; 
           [0023]      FIG. 2  is an assembled sectional view of the secondary battery illustrated in  FIG. 1 ; 
           [0024]      FIG. 3  is an exploded perspective view of a secondary battery, according to another exemplary embodiment of the present disclosure; and 
           [0025]      FIG. 4  is an assembled sectional view of the secondary battery illustrated in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0026]    Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present disclosure, by referring to the figures. 
         [0027]    As those skilled in the art would realize, the described exemplary embodiments may be modified in various different ways, all without departing from the spirit or scope of the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Herein, when a first element is referred to as being formed or disposed “on” a second element, the first element can be disposed directly on the second element, or one or more other elements may be disposed therebetween. When a first element is referred to as being formed or disposed “directly on” a second element, no other elements are disposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the other element or be indirectly connected to the other element, with one or more intervening elements interposed therebetween. 
         [0028]      FIG. 1  is an exploded perspective view of a secondary battery, according to an exemplary embodiment of the present disclosure.  FIG. 2  is an assembled sectional view of the secondary battery illustrated in  FIG. 1 . 
         [0029]    Referring to  FIGS. 1 and 2 , the secondary battery includes an electrode assembly  100 ; a cylindrical can  200  to house the electrode assembly  100  and an electrolyte; and a cap  300  sealing the cylindrical can  200 . Particularly, the cylindrical can  200  and the cap  300  are screwed together. 
         [0030]    The electrode assembly  100  is in the form of a jelly-roll, which is formed by winding a first electrode  110 , a second electrode  130 , and a separator  120  interposed therebetween. The electrode assembly  100  also includes first and second electrode tabs  160  and  180  that respectively extend from opposing ends from the jelly roll. Here, first and second electrodes  110  and  130  have different polarities. For example, if the first electrode  110  is a positive electrode, the second electrode  130  is a negative electrode. In this case, the first electrode tab  160  may be a positive electrode tab, and the second electrode tab  180  may be a negative electrode tab. 
         [0031]    As illustrated in  FIG. 2 , the electrode assembly  100  may further include upper and lower insulation plates  140  and  150  securing electrical stability between the electrode assembly  100  and the cap  300  and/or cylindrical can  200 . In this case, openings through which the first and second electrode tabs  160  and  180  pass may be formed in the upper and lower insulation plates  140  and  150 , respectively. 
         [0032]    The electrode assembly  100  may further include a contact plate  170  positioned between the first electrode tab  160  and the cap  300 , to electrically connect the first electrode tab  160  and the cap  300 . For convenience, the contact plate  170  has been described as a component of the electrode assembly  100 . However, the contact plate  170  and the electrode assembly  100  may be considered as separate components. In addition, the electrode tabs  160  and  180  may be considered as separate components from the electrode assembly  100 . 
         [0033]    The electrode assembly  100  may further include an elastic body  160   a  positioned between the electrodes  110  and  130 , and the contact plate  170 . The elastic body  160   a  applies pressure to the electrode assembly  100 , so that the electrode assembly  100  is stably supported and spaced apart from the contact plate  170 . The elastic body  160   a  may be a metal spring  160   a  that surrounds the first electrode tab  160 . 
         [0034]    The elastic body  160   a  may be formed of a metal having relatively strong corrosion resistance, such as aluminum, nickel, or alloy thereof. However, the elastic body  160   a  is not limited to a spring formed of a metallic material. In particular, the elastic body  160   a  may be implemented using various materials having elasticity and suitable corrosion resistance. 
         [0035]    The cylindrical can  200  accommodates the electrode assembly  100  and the electrolyte, and includes a body  210 , a neck, and an opening. Here, the diameter of the neck is smaller than that of the body  210 . 
         [0036]    The cylindrical can  200  is generally formed of aluminum, iron, or alloy thereof. As illustrated in  FIG. 2 , the bottom surface of the cylindrical can  200  includes a projection  210   a  that contacts the second electrode tab  180 , so that the projection  210   a  itself serves as a negative electrode. A first screw thread  230  is formed on the outer surface of the neck  220 . 
         [0037]    The secondary battery is not limited to having the cylindrical can  200 . That is, the shape of the can  200 , particularly, the shape of the body  210 , may be variously modified, and the neck  220  may be formed in any shape that can be screw-connected to the cap  300 . To put it another way, the shape of a can to house the electrode assembly  100  and an electrolyte is not necessary limited to the above described and shown shape. 
         [0038]    The cap  300  is screw-connected to the neck  220 , so as to be attached to (seal) the cylindrical can  200 . To this end, a second screw thread  310 , to be connected to the first screw thread  230 , is formed on the inner surface of the cap  300 . 
         [0039]    The assembling process of the aforementioned secondary battery will now be described. After the electrode assembly  100  and the electrolyte are inserted into the cylindrical can  200  through the neck  220 , the cylindrical can  200  and the cap  300  are screwed together, by rotating the cap  300  (or the cylindrical can  200 ) along the direction of the screw threads  230  and  310 , while pressing the cap  300  toward the can  200 . Thus, the interior of the cylindrical can  200  is sealed. 
         [0040]    In order to reinforce the connection between the cylindrical can  200  and the cap  300  and effectively seal the interior of the cylindrical can  200 , the cylindrical can  200  and the cap  300  may be adhered to each other with a sealing material  400 , as illustrated in  FIG. 2 . The sealing material  400  may be an adhesive material disposed between the neck  220  and the cap  300 . 
         [0041]    The sealing material  400  may be coated on the outer surface of the neck, or the inner surface of the cap  300 . Once the neck  220  and the cap  300  are screwed together, the sealing material can be heat-fused, to fuse together the neck  200  and the cap  300 . 
         [0042]    The sealing material  400  may be a polypropylene-based material or the like. In the case of the polypropylene material, when gas or heat is generated in the interior of the secondary battery, a polymer layer is melted at a higher temperature than a predetermined temperature, to release the gas. When the internal pressure of the secondary battery is increased, the connection of the cylindrical can  200  and the cap  300  is released, and the cylindrical can  200  is opened. Thus, it is possible to prevent the secondary battery from exploding. The sealing material  400  is not necessarily limited to the polypropylene-based material. That is, the sealing material  400  may be any material that can prevent the secondary battery from exploding. 
         [0043]    The upper and lower portions of the assembled secondary battery can be welded, to secure the electrical stability thereof. For example, the upper portion of the secondary battery may be welded, so that the contact plate  170  electrically connects the first electrode tab  160 , and the cap  300 . That is, the contact plate  170  may be welded to the first electrode tab  160  and the cap  300 . In addition, the lower portion of the secondary battery may be welded, so that the projection  210   a  is electrically connected to the electrode assembly  100 . In particular, the projection  210   a  may be welded to the second electrode tab  180 . 
         [0044]    As described above, the cylindrical can  200  and the cap  300  are screwed together and are adhered to each other with the sealing material  400 , so that it is possible to produce a battery having a simplified structure and a reduced number of components. Accordingly, it is possible to reduce manufacturing costs and to enhance manufacturing efficiency. 
         [0045]    When the elastic body  160   a  is provided between the electrodes  110  and  130 , and the cap  200 , it is possible to properly space and support the electrodes  110  and  130 , and the cap  300 . In other words, the elastic body  160   a  biases the cap  200  away from the electrode assembly  100 . 
         [0046]    When gas is generated in the interior of the secondary battery, and the secondary battery reaches a predetermined temperature, the sealing material  400  melts and the gas is exhausted. In addition, when the internal pressure of the secondary battery reaches a predetermined level, the connection of the cylindrical can  200  and the cap  300  is released, and the cylindrical can  200  is opened. Thus, it is possible to prevent an explosion of the secondary battery. Accordingly, it is possible to secure the stability of the secondary battery. 
         [0047]      FIG. 3  is an exploded perspective view of a secondary battery, according to another exemplary embodiment of the present disclosure.  FIG. 4  is an assembled sectional view of the secondary battery illustrated in  FIG. 3 . In  FIGS. 3 and 4 , similar components have the same reference numerals, and are not described in detail. 
         [0048]    Referring to  FIGS. 3 and 4 , the secondary battery further includes a second elastic body  500 , which may be a heat-resistant sponge. Here, heat resistant refers to having stability at normal battery operating temperatures. The second elastic body  500  is disposed between the electrodes  110  and  130 , and a cap  300  and in particular, between the electrodes  110  and  130  and a contact plate  170 . The second elastic body  500  has an opening through which a first electrode tab  160  and a first elastic body  160   a  extend. 
         [0049]    In addition to the first elastic body  160   a,  the second elastic body  500  stably supports and separates an electrode assembly  100  and the contact plate  170 . The first elastic body  160   a  and a first electrode tab  160  operate as a center pin. However, the first and second elastic bodies  160   a  and  500  may be used together or singularly. 
         [0050]    The second elastic body  500  may be formed of a spongy material, such as a polypropylene-based or polyethylene-based material having excellent electrical properties and shock absorption characteristics. An electrolyte may be absorbed in the second elastic body  500 . In this case, when the electrolyte is exhausted from the secondary battery, due to the long-term use or storage, the electrolyte absorbed in the second elastic body  500  can replace the exhausted electrolyte, by moving into the electrode assembly  100 . Accordingly, the lifetime of the secondary battery can be extended. At this time, an upper insulation plate  140  may be removed or formed of a material through which the electrolyte can permeate. 
         [0051]    Although a few exemplary embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments, without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. For example, the shape of a can to house an electrode assembly and an electrolyte is not necessarily limited to the above description.