Abstract:
A secondary battery includes a case having an interior cavity and an upper opening, an electrode assembly disposed in the interior cavity of the case, a cap assembly, and a vent cover disposed on an outer surface of the cap plate and at least partially covering the safety vent. The cap assembly includes a cap plate and a safety vent formed within the cap plate, the safety vent being thinner than a remainder of the cap plate, and the cap plate coupled with the upper opening of the case. A portion of the vent cover, corresponding in position to the position of the safety vent, is thinner than a remaining portion of the vent cover.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    Embodiments relate to a secondary battery. 
         [0003]    2. Description of the Related Art 
         [0004]    In general, secondary batteries can be charged and discharged, and used repetitively. Secondary batteries are used in such portable electronic devices as mobile phones, laptops, computers, cameras, and camcorders, or used as power sources for driving motors of high-power hybrid electric vehicles, electric vehicles, electric scooters, etc. 
         [0005]    A secondary battery includes an electrode assembly, a case accommodating the electrode assembly, and a cap assembly coupled with an upper portion of the case. 
       SUMMARY 
       [0006]    Embodiments are therefore directed to a secondary battery, which substantially overcome one or more problems due to the limitations and disadvantages of the related art. 
         [0007]    It is therefore a feature of an embodiment to provide a secondary battery that includes a vent cover to protect a safety vent before the safety vent is in operation. 
         [0008]    It is therefore another feature of an embodiment to provide a secondary battery that allows gas to be discharged when the safety vent is in operation. 
         [0009]    Embodiments may be realized by providing a secondary battery including a case having an interior cavity and an upper opening, an electrode assembly disposed in the interior cavity of the case, a cap assembly, and a vent cover disposed on an outer surface of the cap plate and at least partially covering the safety vent. The cap assembly may include a cap plate and a safety vent formed within the cap plate, the safety vent being thinner than a remainder of the cap plate, and the cap plate coupled with the upper opening of the case. A portion of the vent cover corresponding in position to the position of the safety vent may be thinner than a remaining portion of the vent cover. 
         [0010]    According to some embodiments, the vent cover may include at least one of a groove or notch on a surface of the vent cover facing the safety vent. According to some embodiments, the groove may have a shape that is identical to a shape of the safety vent. According to some embodiments, the groove may include a first groove and a second groove, and the second groove may be intersecting with the first groove. According to some embodiments, the first groove and the second groove may intersect orthogonally. According to some embodiments, the first groove and the second groove may be linear. 
         [0011]    According to some embodiments, the first groove and the second groove are a plurality of dotted lines. According to some embodiments, the groove may include a first groove disposed at a center of the vent cover and a second groove and a third groove which extend from both ends of the first groove toward corners of the vent cover. According to some embodiments, the first groove, the second groove, and the third groove may be linear. 
         [0012]    According to some embodiments, the groove may include a branched groove having a main groove, and first and second V-shaped grooves extending from opposing ends of the main groove. According to some embodiments, the main groove may be in a center of the vent cover and the V-shaped grooves may extend towards corners of the vent cover. According to some embodiments, the groove may be linear. 
         [0013]    According to some embodiments, the notch may include a first notch and a second notch, the first notch and the second notch may be intersecting each other. According to some embodiments, the first notch and the second notch may intersect orthogonally. According to some embodiments, the first notch and the second notch may be a plurality of dotted lines. According to some embodiments, the plurality of notches may include a first plurality of notches arranged in a first line and a second plurality of notches arranged in a second line. The first and second lines may be intersecting. According to some embodiments, the first and second lines may intersect orthogonally. 
         [0014]    According to some embodiments, the notch may include a branched notch having a main notch, and first and second V-shaped notches extending from opposing ends of the main notches. According to some embodiments, the notch may be linear. According to some embodiments, the vent cover may be formed of an insulating material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above and other features and advantages will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, in which: 
           [0016]      FIG. 1  illustrates a perspective view of a secondary battery according to an embodiment in a disassembled state; 
           [0017]      FIG. 2  illustrates a perspective view of the secondary battery of  FIG. 1  in an assembled state; 
           [0018]      FIG. 3  illustrates a sectional view of a vent cover of the secondary battery of  FIG. 2 ; 
           [0019]      FIG. 4  illustrates an enlarged perspective view of the vent cover of the secondary battery of  FIG. 2 ; 
           [0020]      FIG. 5A  illustrates an enlarged perspective view of a vent cover of a secondary battery according to another embodiment; 
           [0021]      FIG. 5B  illustrates an enlarged perspective view of a vent cover of a secondary battery according to another embodiment; 
           [0022]      FIG. 6A  illustrates an enlarged perspective view of a vent cover of a secondary battery according to another embodiment; 
           [0023]      FIG. 6B  illustrates an enlarged perspective view of a vent cover of a secondary battery according to another embodiment; 
           [0024]      FIG. 7A  illustrates an enlarged perspective view of a vent cover of a secondary battery according to another embodiment; and 
           [0025]      FIG. 7B  illustrates an enlarged perspective view of a vent cover of a secondary battery according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Korean Patent Application No. 10-2011-0014658 filed on Feb. 18, 2011, in the Korean Intellectual Property Office, and entitled: “Secondary Battery” is incorporated by reference herein in its entirety. 
         [0027]    Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0028]    In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout. 
         [0029]    Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 
         [0030]      FIG. 1  is a perspective view illustrating a secondary battery according to an embodiment in a disassembled state, and  FIG. 2  is a perspective view illustrating the secondary battery of  FIG. 1  in an assembled state.  FIG. 3  is a sectional view illustrating a vent cover of the secondary battery of  FIG. 2 , and  FIG. 4  is an enlarged perspective view illustrating the vent cover of the secondary battery of  FIG. 2 . Here,  FIG. 4  illustrates a state in which a lower surface of the vent cover faces upwards. 
         [0031]    Referring to  FIGS. 1 and 2 , a secondary battery  100  of the current embodiment may include an electrode assembly  110 , a case  120 , a cap assembly  130 , an insulating case  140 , and a vent cover  150 . 
         [0032]    The electrode assembly  110  may be a laminate formed by winding or overlapping a first electrode plate  111 , a separator  113 , and a second electrode plate  112 . The first electrode plate  111 , the separator  113 , and the second electrode plate  112  may each be formed as a thin plate or film. In addition, the electrode assembly  110  may include a first electrode tab  114  and a second electrode tab  115 . 
         [0033]    The first electrode plate  111  may include a first electrode collector. The first electrode collector may be formed of aluminum foil. A first electrode active material may be disposed in the first electrode collector. A material such as lithium cobalt oxide may be used as the first electrode active material. 
         [0034]    The second electrode plate  112  may include a second electrode collector formed of copper foil, and a second electrode active material disposed in the second electrode collector. A material such as carbon may be used as the second electrode active material. 
         [0035]    The first electrode plate  111  may be positive electrode, and the second electrode plate  112  may be negative electrode. In addition, the first electrode plate  111  and the second electrode plate  112  may have different polarities. 
         [0036]    The separator  113  may be formed of polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene. The separator  113  may have a larger width than the first electrode plate  111  and the second electrode plate  112  to prevent a short circuit between the electrode plates. According to some embodiments, the separator  113  may have a larger width than the combined widths of the first electrode plate  111  and the second electrode plate  112 . According to some embodiments, the separator  113  may have a larger width than the width of the first electrode plate  111 . According to some embodiments, the separator  113  may have a larger width than the width of the second electrode plate  112 . 
         [0037]      FIG. 1  shows the first electrode tab  114  and the second electrode tab  115  extending out of the first electrode plate  111  and the second electrode plate  112 , respectively. The first electrode tab  114  and the second electrode tab  115  may be disposed in the first electrode plate  111  and the second electrode plate  112 , respectively. The first electrode tab  114  may be pulled to extend out of the first electrode plate  111 . The second electrode tab  115  may be pulled to extend out of the second electrode plate  112 . Insulating tape  116   a  may be provided at boundary portions or edge portions of the first electrode plate  111  from which the first electrode tab  114  extends. Insulating tape  116   b  may be provided at boundary or portions or edge portions of the second electrode plate  112  from which the second electrode tab  115  extends. Insulating tapes  116   a  and  116   b  may prevent short circuit between the electrode plates. 
         [0038]    The case  120  may be a metal can. The case  120  may be formed by a processing method such as deep drawing. The case  120  may be formed of such a lightweight conductive metal as aluminum or aluminum alloy. Thus, the case  120  may act as an electrode. According to some embodiments, the case  120  may act as a positive electrode. The case  120  may contain the electrode assembly  110  and an electrolyte. An upper opening of the case  120 , which is configured to receive the electrode assembly  110 , may be sealed with the cap assembly  130 . 
         [0039]    The cap assembly  130  may include a cap plate  131 , a stopper  134 , a safety vent  135 , and an electrode terminal  136 . 
         [0040]    The cap plate  131  may be a metal plate having a size and a shape corresponding to a size and a shape of the upper opening of the case  120 . The cap plate  131  may be coupled with the case  120  by, for example, welding, and may act as a positive electrode like the case  120 . A terminal hole  132  may be disposed at a center of the cap plate  131 . In addition, an electrolyte inlet  133  may be defined in the cap plate  131  proximate a first end of the cap plate  131 . 
         [0041]    The electrolyte may be injected into the case  120  through the electrolyte inlet  133 . The stopper  134  may be configured to seal the electrolyte inlet  133  after the electrolyte is injected into the case  120 . In general, the stopper  134  may be ball-shaped base metal. The metal may be aluminum or a metal containing aluminum. The stopper  134  may be pressed into the electrolyte inlet  133  mechanically, and engage the electrolyte inlet  133 . 
         [0042]    The safety vent  135  may be disposed in the cap plate  131 , proximate a second end of the cap plate, which opposes the first end of the cap plate  131 . The safety vent  135  may further protect the secondary battery  100  by discharging gas when an internal pressure of the secondary battery  100  is larger than a reference pressure, for example, due to overcharge. 
         [0043]    The electrode terminal  136  may pass through the cap plate  131  via the terminal hole  132 . The electrode terminal  136  may be inserted into a tube-shaped gasket  137  prior to insertion in the terminal hole  132 . The tube-shaped gasket may cover or surround at least a portion of an outer surface of the electrode terminal  136  to insulate the electrode terminal  136  and the cap plate  131 . An insulating plate  138  may be disposed on a lower surface of the cap plate  131 , and a terminal plate  139  may be disposed on a lower surface of the insulating plate  138 . A bottom surface of the electrode terminal  136  may be electrically connected to the terminal plate  139 . The electrode terminal  136  may be electrically connected to the second electrode plate  112  of the electrode assembly  110  through the second electrode tab  115  of the electrode assembly  110 . The first electrode plate  111  of the electrode assembly  110  may be electrically connected to the cap plate  131  through the first electrode tab  114 . 
         [0044]    The insulating case  140  may be disposed between the electrode assembly  110  and the cap assembly  130 . The insulating case  140  may prevent an electric short circuit between the electrode assembly  110  and the cap assembly  130 , and may support and/or fix the first electrode tab  114  and the second electrode tab  115 . Therefore, the insulating case  140  may be formed of an insulating material. 
         [0045]    The vent cover  150  may be disposed on an outer surface of the cap plate  131  to cover the safety vent  135 . When, for example, an upper cover using a hot-melting resin is disposed on the cap plate  131 , the vent cover  150  may protect the safety vent  135  from a melting pressure of the hot-melting resin, and may prevent the safety vent  135  from being damaged by the melting pressure. In addition, the vent cover  150  may prevent the safety vent  135  from being damaged by an external force before the safety vent  135  is put into operation. 
         [0046]    Hereinafter, the safety vent  135  and the vent cover  150  are described in more detail. The safety vent  135  may include an indented portion or thinner portion of the cap plate  131 , as shown more clearly in  FIG. 3 . The safety vent  135  may be formed by providing a groove in the top surface, bottom surface, or both top and bottom surfaces of the cap plate  131 . The safety vent  135  may be fractured first when the internal pressure of the secondary battery  100  is larger than the reference pressure, to facilitate discharge of gas. 
         [0047]    Referring to  FIGS. 3 and 4 , at least a part of the vent cover  150  corresponding to or aligned with the safety vent  135  may be thinner than the rest of the vent cover  150 . According to an embodiment, the vent cover  150  may include a groove  151  disposed on a surface facing the safety vent  135 . The vent cover  150  may protect the safety vent  135  before the safety vent  135  is in operation. When the safety vent  135  is in operation and is fractured, the groove  151  may be fractured to facilitate discharge of gas out of the secondary battery  100  through the vent cover  150 . 
         [0048]    Although the groove  151  is illustrated as having a smaller size than the safety vent  135 , the groove  151  may be bigger than the safety vent  135 . The groove  151  may have a shape identical to a shape of the safety vent  135  and may be disposed at a position corresponding to the safety vent  135 , so that gas may be discharged more efficiently. The vent cover  150  may be formed of an insulating material such as insulating tape. 
         [0049]    As described above, the secondary battery  100  according to an embodiment including the vent cover  150 , may have the groove  151  defined therein, so that at least the part of the vent cover  150  corresponding to the safety vent  135  is thinner than the rest of the vent cover  150 . The vent cover  150  may protect the safety vent  135  before the safety vent  135  is in operation. When the safety vent  135  is in operation and is fractured, the groove  151  may be fractured to facilitate discharge of gas out of the secondary battery  100  through the vent cover  150 . Therefore, the secondary battery  100  according to the embodiment may provide increased stability. 
         [0050]    A secondary battery will now be described according to another embodiment.  FIGS. 5A and 5B  are enlarged perspective views illustrating another embodiment of a vent cover of the secondary battery, which is designated  250 .  FIGS. 5A and 5B  illustrate a lower surface of the vent cover  250  facing upwards. The secondary battery may include the vent cover  250  instead of the vent cover  150 , and all other components, as well as the function of the secondary battery, may be as described above for the secondary battery of  FIG. 1 . Therefore, the description that immediately follows relates primarily to the vent cover  250 . 
         [0051]    Referring to  FIG. 5A , the vent cover  250  may be similar to the vent cover  150  except that the vent cover  150  may have an X-shaped groove  251  instead of the groove  151 . The X-shaped groove  251  of the vent cover  250  may include a first rectangular groove  252  and a second rectangular groove  253 , which intersect each other to form an X shape. Each of the first rectangular groove  252  and the second rectangular groove  253  can have a narrow width. Pressure created by gas that is discharged from the safety vent  135  when the safety vent  135  is in operation and is fractured, may be concentrated on the groove  251 , resulting in fracturing of the vent cover  250 . 
         [0052]    Although  FIG. 5A  illustrates the vent cover  250  with grooves  251  that have a predetermined width, the vent cover  250  may, instead, be simply configured to include an X-shaped notch  251   a,  as shown in  FIG. 5B . In other words, the notch  251   a  may simply be narrow or be formed without controlling for a predetermined width or depth. In this case, the X-shaped notch  251   a  may include a first notch  252   a  and a second notch  253   a,  which intersect each other to form an X-shape. 
         [0053]    As described above, the secondary battery according to an embodiment having the vent cover  250 , may have an X-shaped groove  251  or an X-shaped notch defined in the vent cover  250 , to facilitate fracturing of the vent cover  250  to discharge gas when the safety vent  135  is in operation and is fractured. Therefore, the secondary battery according to the embodiment may provide increased stability. 
         [0054]    A secondary battery will now be described according to another embodiment.  FIGS. 6A and 6B  are enlarged perspective views of another embodiment of a vent cover of the secondary battery, which is designated  350  in the figures. Here,  FIGS. 6A and 6B  illustrates a lower surface of the vent cover, facing upwards. The secondary battery may include the vent cover  350  instead of the vent cover  150 , and all other components, as well as the function of the secondary battery, may be as described above for the secondary battery of  FIG. 1 . Therefore, the description that immediately follows relates primarily to the vent cover  350 . 
         [0055]    Referring to  FIG. 6A , the vent cover  350  may be similar to the vent cover  150  except that the vent cover  350  may include an X-shaped arrangement of a plurality of grooves  351  instead of the groove  151 . The X-shaped arrangement of a plurality of grooves  351  may include a first plurality of grooves  352  and a second plurality of grooves  353 . The first plurality of grooves  352  may include a first set of individual grooves aligned in a linear fashion with respect to one another. The second plurality of grooves  353  may include a second set of individual grooves aligned in a linear fashion with respect to one another. The first plurality of grooves  352  and the second plurality of grooves  353  may intersect each other to form an X shape. Each individual groove of the first plurality of grooves  352  and the second plurality of grooves  353  can have a narrow width. Pressure created by gas that is discharged from the safety vent  135  when the safety vent  135  is in operation and is fractured, may be concentrated on the groove  351 , resulting in fracturing of the vent cover  350 . Even when the pressure created by the gas discharged from the safety vent  135  is weak, the fracturing of the vent cover  350  may be facilitated. In other words, the reference pressure which is set to put the safety vent  135  into operation is adjustable. 
         [0056]    Although  FIG. 6A  illustrates the vent cover  350  including the X-shaped arrangement of a plurality of grooves  351  which has a predetermined width, the vent cover  350  may, instead, be simply configured to include an X-shaped arrangement of a plurality of notches  351   a,  as shown in  FIG. 6B . In this case, the X-shaped arrangement of a plurality of notches  351   a  may include a first plurality of notches  352   a  and a second plurality of notches  353   a,  which intersect each other to form an X-shape. 
         [0057]    As described above, the secondary battery according to an embodiment having the vent cover  350 , may have an X-shaped arrangement of a plurality of grooves, to facilitate fracturing of the vent cover  350  to discharge gas when the safety vent  135  is in operation and is fractured. Even when the pressure created by the gas discharged from the safety vent  135  is weak, the fracturing of the vent cover  350  may be facilitated. Therefore, the secondary battery according to the embodiment may provide increased stability. 
         [0058]    A secondary battery will now be described according to another embodiment.  FIGS. 7A and 7B  are enlarged perspective views illustrating another embodiment of a vent cover of the secondary battery, which is designated  450  in the figures. Here,  FIGS. 7A and 7B  illustrate a lower surface of the vent cover  450 , facing upwards. The secondary battery may include the vent cover  450  instead of the vent cover  150 , and all other components, as well as the function of the secondary battery, may be as described above for the secondary battery of  FIG. 1 . Therefore, the description that immediately follows relates primarily to the vent cover  450 . 
         [0059]    Referring to  FIG. 7A , the vent cover  450  may be similar to the vent cover  150  except that the vent cover  450  may include a branched groove  451  instead of the groove  151 . The branched groove  451  may include a rectangular main groove  452  having first and second opposing ends, a first V-shaped groove  453  extending from the first end toward a first edge of the vent cover  450 , and a second V-shaped groove  454  extending from the second end toward a second, opposing edge of the vent cover  450 . Specifically, the rectangular main groove  452  may extend horizontally across a center of the vent cover  450 . The branched groove  451  may have a narrow width. Pressure created by the gas discharged from the safety vent  135  when the safety vent  135  is in operation and is fractured, may be concentrated on the rectangular main groove  452 , resulting in fracturing of the vent cover  350 . In addition, the first V-shaped groove  453  and the second V-shaped groove  454  may be fractured when the rectangular main groove  454  is fractured, and an area through which the gas of the secondary battery may be discharged may be widened. 
         [0060]    Although  FIG. 7A  illustrates the vent cover  450  including the branched groove  451  which has a predetermined width, the vent cover  450  may, instead, be simply configured to include a branched notch  451   a,  as shown in  FIG. 7B . In this case, the branched notch  451   a  includes a first V-shaped notch  453   a  and a second V-shaped notch  454   a  that extend from opposing ends of a rectangular main notch  451   a.    
         [0061]    As described above, the secondary battery according to an embodiment having the vent cover  450  having the branched groove  451  or the branched notch  451   a,  may easily discharge gas by facilitating fracturing of the vent cover  450  and by widening the area through which the gas of the secondary battery is discharged when the safety vent  135  is in operation and is fractured. Therefore, the secondary battery according to the embodiment may provide increased stability. 
         [0062]    The secondary battery according to various embodiments, which includes the vent cover having a groove, so that at least the part of the vent cover corresponding to the safety vent is thinner than the rest of the vent cover, may protect the safety vent before the safety vent is put into operation. The secondary battery may easily discharge gas by facilitating the fracturing of the vent cover when the safety vent is in operation and is fractured. Therefore, the secondary battery according to embodiments may provide increased stability. 
         [0063]    Example 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. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.