Abstract:
A secondary battery includes: a cylindrical can including a first region, a second region, and a first bent portion extending between the first region and the second region on a circumferential surface of the can; an electrode assembly accommodated in the can; and a cap assembly at a top end of the can and sealing the can. The first bent portion is bent such that an angle between the first region and the second region is in a range of about 90° to about 100°; the first region of the can partially covers a top surface of the cap assembly facing an exterior side of the can, and the second region of the can surrounds side surfaces of the cap assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0045539, filed on 14 Apr. 2016 in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. §119, the content of which is herein incorporated by reference in its entirety. 
       BACKGROUND 
     1. Field 
       [0002]    Embodiments of the present invention relate to a secondary battery. 
       2. Description of the Related Art 
       [0003]    A secondary battery is a battery that converts chemical energy into electrical energy to supply power to an external circuit and converts electrical energy into chemical energy when it is supplied with external power to store electricity that can be later discharged. The secondary battery is widely used for a variety of electric devices and/or electric vehicles. The secondary battery may be classified as a cylindrical battery, a prismatic battery, or a pouch type battery according to the external shape and/or construction thereof. Among other features, the cylindrical battery has a relatively large capacity and good structural stability. 
         [0004]    The above information disclosed in this Background section is for enhancement of understanding of the background of the described technology, and therefore, it may contain information that does not form prior art. 
       SUMMARY 
       [0005]    Embodiments of the present invention provide a secondary battery in which a circumferential surface of a can will not rupture, or will have a reduced risk of a rupture, due to internal gas generated by the secondary battery. 
         [0006]    The above and other aspects of the present invention will be described in or will be apparent from the following description of exemplary embodiments thereof. 
         [0007]    According to an embodiment of the present invention, a secondary battery includes: a cylindrical can including a first region, a second region, and a first bent portion extending between the first region and the second region on a circumferential surface of the can; an electrode assembly accommodated in the can; and a cap assembly at a top end of the can and sealing the can. The first region of the can partially covers a top surface of the cap assembly facing an exterior side of the can, the second region of the can surrounds side surfaces of the cap assembly, and the first bent portion is bent such that an angle between the first region and the second region is in a range of about 90° to about 100°. 
         [0008]    In an embodiment, the first bent portion may include a notch. 
         [0009]    In an embodiment, the second region may include a notch. 
         [0010]    In an embodiment, each of the first bent portion and the second region may include a notch. 
         [0011]    The can may further include a beading part and a second bent portion on the circumferential surface of the can. The beading part may be inwardly recessed to support a bottom surface of the cap assembly facing an interior side of the can, and the second bent portion may extend between the second region and the beading part and may include a notch. 
         [0012]    In an embodiment, the first bent region may include a notch. 
         [0013]    In an embodiment, the second region may include a notch. 
         [0014]    In an embodiment, each of the first bent portion and the second region may include a notch. 
         [0015]    As described above, in a secondary battery according to an embodiment of the present invention, a first bent portion is bent and extends between a first region and a second region such that an angle between the first region and the second region is in a range of about 90° to about 100°, the first region covers (e.g., partially covers) a top surface of the cap assembly, and the second region surrounds side surfaces of the cap assembly so that the first bent portion may unfold to allow the cap assembly to separate from a can before internal gas generated in the can ruptures a circumferential surface of the can, thereby preventing the circumferential surface of the can from rupturing. 
         [0016]    In some embodiments of the present invention, the circumferential surface of the can includes a notch to allow the circumferential surface of the can to be easily transformed around the notch, thereby ensuring that the cap assembly can separate from the can. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other features of the present invention will become more apparent by describing, in detail, exemplary embodiments thereof with reference to the attached drawings in which: 
           [0018]      FIG. 1  is a cut-away exploded perspective view of a secondary battery according to an embodiment of the present invention; 
           [0019]      FIG. 2  is a cross-sectional view of the portion ‘A’ of  FIG. 1 ; 
           [0020]      FIG. 3  is a schematic view illustrating a state in which a cap assembly is separated from a can of a secondary battery according to an embodiment of the present invention; and 
           [0021]      FIG. 4  is a partial cross-sectional view of a secondary battery according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Hereinafter, exemplary embodiments of the present invention will be described, in detail, with reference to the accompanying drawings such that they can easily be made and used by those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as being 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 concept of the present invention to those skilled in the art. The present invention will be defined by the appended claims and their equivalents. 
         [0023]    In the drawings, thicknesses of layers and regions may be exaggerated for clarity. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. In addition, it will be understood that when an element A is referred to as being “coupled to” or “connected to” an element B, the element A can be directly coupled or connected to the element B or an intervening element C may be present between the elements A and B so that the element A can be indirectly coupled or connected to the element B. 
         [0024]    In addition, the terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting thereof. As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” or “include” and/or “comprising” or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, the use of “may” when describing embodiments of the present invention relates to “one or more embodiments of the present invention.” Expressions, such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Also, the term “exemplary” is intended to refer to an example or illustration. As used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively. 
         [0025]    It will be understood that, although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers, and/or sections, these members, elements, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer, and/or section from another. Thus, for example, a first member, a first element, a first region, a first layer, and/or a first section discussed below could be termed a second member, a second element, a second region, a second layer, and/or a second section without departing from the teachings. 
         [0026]    Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. 
         [0027]    Also, any numerical range disclosed and/or recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of “1.0 to 10.0” is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than  10 . 0 , such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein, and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. All such ranges are intended to be inherently described in this specification such that amending to expressly recite any such subranges would comply with the requirements of 35 U.S.C. §112(a) and 35 U.S.C. §132(a). 
         [0028]      FIG. 1  is a cut-away exploded perspective view of a secondary battery  100  according to an embodiment of the present invention. 
         [0029]    Referring to  FIG. 1 , the secondary battery  100  includes a can  110 , an electrode assembly  120 , and a cap assembly  130 . 
         [0030]    The can  110  has a cylinder shape having an open top end. The can  110  is generally made of steel, aluminum, or a combination thereof. However, the can  110  may be made of any suitable material other than the materials listed herein. 
         [0031]    The electrode assembly  120  includes a positive electrode plate  121  having a positive electrode active material coated on a positive electrode current collector, a negative electrode plate  122  having a negative electrode active material coated on a negative electrode current collector, and a separator  123  disposed between the positive electrode plate  121  and the negative electrode plate  122  to electrically insulate the positive electrode plate  121  and the negative electrode plate  122  from each other. The electrode assembly  120  is (e.g., the positive electrode plate  121 , the negative electrode plate  122 , and the separator  123  are) wound in a jelly-roll configuration. A positive electrode uncoated portion  121   a  that is not coated with the positive electrode active material is formed at an end of the positive electrode current collector, and a positive electrode tab  121   b  is coupled to the positive electrode uncoated portion  121   a.  Likewise, a negative electrode uncoated portion  122   a  that is not coated with the negative electrode active material is formed at an end of the negative electrode current collector, and a negative electrode tab  122   b  is coupled to the negative electrode uncoated portion  122   a.  The electrode assembly  120  is accommodated inside the can  110 . In some embodiments, the negative electrode tab  122   b  may be connected to a bottom surface of the can  110 . In these embodiments, the bottom surface of the can  110  may serve as a negative electrode terminal. 
         [0032]    The cap assembly  130  is disposed at the top end of the can  110  and seals the can  110 . The cap assembly  130  includes a cap-up  131 , a safety device  132 , and a safety vent  133 . 
         [0033]    A terminal portion  131   a  upwardly convexly protrudes from the cap-up  131 . In addition, an exhaust opening  131   b  (e.g., an exhaust hole) is formed around the terminal portion  131   a.  When an over-charge condition or other abnormal operation of the secondary battery  100  occurs, heat and gases may be generated in the can  110 . In this case, the exhaust opening  131   b  may exhaust the gases to the outside. 
         [0034]    The safety device  132  may be disposed beneath the cap-up  131 . In some embodiments, the safety device  132  is a PTC element having increasing resistance according to a temperature increase. The safety device  132  may prevent current from flowing (or may reduce current flow) between the positive electrode tab  121   b  of the electrode assembly  120  and the cap-up  131  due to its resistance increasing when the secondary battery  100  is over-heated, thereby preventing the secondary battery  100  from being further over-heated. 
         [0035]    The safety vent  133  may be disposed beneath the safety device  132  to be connected to the positive electrode tab  121   b  of the electrode assembly  120 . A rupture groove  133   a  is formed in the safety vent  133 . When the gases press the safety vent  133 , the safety vent  133  may be ruptured along the rupture groove  133   a.  In this case, the gases are exhausted through gaps resulting from the rupture and are eventually released through the exhaust opening  131   b  in the cap-up  131 . 
         [0036]    Insulation plates may further be installed between each of the cap-up  131 , the safety device  132 , and the safety vent  133 , and an insulation gasket G may further be coupled to a side surface of the cap assembly  130 . 
         [0037]    The aforementioned configuration of the safety vent  133  may effectively function to exhaust a relatively small amount of gas. However, in this configuration, it may be difficult to effectively cope with a problem that may be caused when excessive heat and gas are instantaneously generated in the can  110 . In this case, the circumferential surface of the can  110  may be pressed by the gas that is not exhausted from the inside to the outside of the can  110 , thereby causing the circumferential surface of the can  110  to rupture, which may be referred to as a side-rupture. In a case where a plurality of secondary batteries constitute a module and the circumferential surface of the can  110  of one of the secondary batteries constituting the module ruptures, a can of another secondary battery that is adjacent to the can  110  may also rupture, resulting in successive explosions of the secondary batteries (so-called side-rupture propagation). Therefore, a configuration of the can  110  which can prevent the circumferential surface of the can  110  from rupturing (or which can reduce the occurrence of the circumferential surface of the can  110  rupturing) will be further described below. 
         [0038]      FIG. 2  is a cross-sectional view of the portion ‘A’ of  FIG. 1 . 
         [0039]    Referring to  FIG. 2 , a first region  111 , a second region  112 , a first bent portion  113 , a beading portion  114 , and a second bent portion  115  are formed on the circumferential surface of the can  110 . 
         [0040]    The first region  111  covers (e.g., partially covers) a surface of the cap assembly  130  that faces the outside of the can  110 , for example, the top surface of the cap assembly  130 . The first region  111  may prevent the cap assembly  130  from being arbitrarily separated from the can  110 . 
         [0041]    The second region  112  surrounds the side surface of the cap assembly  130 . 
         [0042]    The first bent portion  113  is bent to connect the first region  111  and the second region  112  to each other (e.g., the first bent portion  113  extends between the first region  111  and the second region  112 ). 
         [0043]    The beading portion  114  is a portion of the can  110  that is concavely recessed toward the inside of the can  110  so as to support a surface of the cap assembly  130  that faces the inside of the can  110 , for example, the bottom surface of the cap assembly  130 , and the second bent portion  115  is bent to connect the second region  112  and the beading portion  114  to each other (e.g., the second bent portion  115  extends between the second region  112  and the beading portion  114 ). 
         [0044]    In some embodiments, the first bent portion  113  may be bent such that an angle (θ) formed between the first region  111  and the second region  112  is in a range of about 90° to about 100°. 
         [0045]    When the first bent portion  113  is bent such that the angle (θ) formed between the first region  111  and the second region  112  is about 90° or greater, the angle (θ) formed between the first region  111  and the second region  112  can be more easily increased (e.g., can be increased with less pressure) than in a conventional case in which a first bent portion is bent such that the angle (θ) formed between a first region and a second region is less than about 90°. For example, the first bent portion  113  can be more easily unfolded by a relatively small force. Thus, a cap assembly  130  can be more easily separated from the can  110  even when a relatively low pressure is applied to the cap assembly  130 , as shown in  FIG. 3 . Therefore, the first bent portion  113  may be unfolded so as to allow the cap assembly  130  to separate from the can  110  before the internal gas ruptures the circumferential surface of the can  110 , and the gas may be smoothly exhausted through the top end of the can  110 , thereby preventing the circumferential surface of the can  110  from rupturing or reducing the chance of the circumferential surface of the can  110  rupturing. 
         [0046]    When the first bent portion  113  is bent such that the angle (θ) formed between the first region  111  and the second region  112  is about 100° or less, the cap assembly  130  may not be arbitrarily separated from or move away from the can  110 . 
         [0047]    In addition, a notch N may be formed in the first bent portion  113 . 
         [0048]    Because the first bent portion  113  is more easily unfolded around the notch N, it is possible to ensure that the first bent portion  113  is unfolded (e.g., it is possible to reduce the pressure or force necessary to unfold the first bent portion  113 ) so that the cap assembly  130  can separate from the can  110  before the gas ruptures the circumferential surface of the can  110 . 
         [0049]    The notch N may include a plurality of notches formed along (e.g., successively arranged along) the circumference of the can  110 . Alternatively, the notch N may include a plurality of notches formed along a length of the can  110 . 
         [0050]      FIG. 4  is a partial cross-sectional view of a secondary battery  200  according to another embodiment of the present invention. Functional elements shown in  FIG. 4  are substantially the same as corresponding functional elements shown in  FIG. 2 . 
         [0051]    Referring to  FIG. 4 , the secondary battery  200  according to another embodiment of the present invention is different from the secondary battery  100  according to the previously-described embodiment of the present invention in that a notch N is formed in a second region  212  and/or in a second bent portion  215 . 
         [0052]    In the secondary battery  200  according to another embodiment of the present invention, the second region  212  and/or the second bent portion  215  may be easily bent around the notch N so as to face the outside of a can  210 . Therefore, because a configuration in which a cap assembly  230  is allowed to separate from the can  210  is more easily provided or secured, it is possible to ensure that the cap assembly  230  can separate from the can  210  before the internal gas ruptures the circumferential surface of the can  210 . 
         [0053]    While secondary batteries according to exemplary embodiments of the present invention have been particularly shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents.