Abstract:
A rechargeable battery includes an electrode assembly including first and second electrodes; a case accommodating the electrode assembly; a cap plate having a short-circuit opening; a first terminal coupled to the first electrode; a second terminal coupled to the second electrode; and a short-circuit member at the cap plate, corresponding to the short-circuit opening, and configured to deform to electrically couple the first and second electrodes; and a short-circuit protrusion at the second terminal and configured to contact the short-circuit member, wherein a surface roughness of the short-circuit protrusion is greater than that of the cap plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0119955 filed in the Korean Intellectual Property Office on Oct. 8, 2013, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The described technology relates generally to a rechargeable battery. 
         [0004]    2. Description of the Related Art 
         [0005]    A rechargeable battery differs from a primary battery in that it is designed to be repeatedly charged and discharged, while the latter is not designed to be recharged. 
         [0006]    A low-capacity rechargeable battery is used in, for example, small portable electronic devices such as mobile phones, laptop computers, and camcorders, while a high-capacity rechargeable battery is used as, for example, a power source for driving a motor of a hybrid vehicle and the like. 
         [0007]    Recently, a high power rechargeable battery using a non-aqueous electrolyte and having high energy density has been developed, and the high power rechargeable battery is formed by coupling a plurality of rechargeable batteries in series to be used as a power source for driving a motor of a device requiring a large amount of electric power, for example, an electric vehicle and the like. 
         [0008]    In addition, a high-capacity rechargeable battery may include a plurality of rechargeable batteries connected in series, and each rechargeable battery may be formed in, for example, a cylindrical shape, a prismatic shape, and the like. 
         [0009]    When internal pressure of one of the rechargeable batteries, with its case made of, for example, metal and the like, is increased due to, for example, an abnormal reaction, the rechargeable battery may explode or catch fire. 
         [0010]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0011]    Accordingly, embodiments of the present invention provide a rechargeable battery having reduced contact resistance when a short-circuit occurs to prevent the rechargeable battery from exploding or catching fire. 
         [0012]    A rechargeable battery according to an example embodiment includes an electrode assembly including first and second electrodes; a case accommodating the electrode assembly; a cap plate on the case and having a short-circuit opening; a first terminal coupled to the first electrode; a second terminal coupled to the second electrode; a short-circuit member at the cap plate, corresponding to the short-circuit opening, and configured to deform to electrically couple the first and second electrodes; and a short-circuit protrusion at the second terminal and configured to contact the short-circuit member, wherein a surface roughness of the short-circuit protrusion is greater than that of the cap plate. 
         [0013]    The shaft-circuit protrusion may be integrally formed with and may protrude from the second terminal. 
         [0014]    The surface roughness of the second terminal may be greater than that of the cap plate. 
         [0015]    The surface roughness of the short-circuit protrusion may be greater than that of parts of the second terminal other than the short-circuit protrusion. 
         [0016]    The second terminal may include a plurality of micro-sized protrusions. 
         [0017]    The plurality of micro-sized protrusions may be only on the short-circuit protrusion of the second terminal. 
         [0018]    The surface roughness of the short-circuit protrusion may be about 1.3 to about 10 times greater than that of the cap plate. 
         [0019]    The average length of micro-sized protrusions producing the surface roughness of the short-circuit protrusions may be about 0.5 μm to about 100 μm. 
         [0020]    The short-circuit protrusions may protrude in a ring shape. 
         [0021]    The short-circuit protrusions may be etched by an acid or a base, or may be sandblasted. 
         [0022]    The short-circuit protrusions may be processed by stamping using a stamp comprising micro-sized protrusions. 
         [0023]    The short-circuit protrusion may be coupled to and may protrude from the second terminal. 
         [0024]    The surface roughness of the short-circuit protrusion may be greater than that of the parts of the second terminal other than the short-circuit protrusion. 
         [0025]    According to an example embodiment, because the surface roughness of the short-circuit protrusion is increased, contact resistance is reduced when the short-circuit member contacts the short-circuit protrusion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a perspective view of a rechargeable battery according to a first example embodiment. 
           [0027]      FIG. 2  is a cross-sectional view of  FIG. 1 , taken along the line II-II. 
           [0028]      FIG. 3  is a partially cut-away perspective view of the rechargeable battery according to the first example embodiment. 
           [0029]      FIG. 4  is a perspective view of a second terminal viewed from the bottom according to the first example embodiment. 
           [0030]      FIG. 5A  is a photograph showing a part of the second terminal before the surface processing, and  FIG. 5B  is a photograph showing the part of the second terminal after the surface processing. 
           [0031]      FIG. 6  is a perspective view of a second terminal viewed from the bottom according to a second example embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the invention are shown. 
         [0033]    As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
         [0034]    Like reference numerals designate like elements throughout the specification and the drawings. It will be understood that when an element or layer is referred to as being “on” or “connected to” another element or layer, it may be directly on or connected to the other element or layer or intervening elements or layers may be present. When an element is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Further, the use of “may” when describing embodiments of the present invention refers to “one or more embodiments of the present invention.” 
         [0035]      FIG. 1  is a perspective view of a rechargeable battery according to a first example embodiment, and  FIG. 2  is a cross-sectional view of  FIG. 1 , taken along the line II-II. 
         [0036]    Referring to  FIG. 1  and  FIG. 2 , the rechargeable battery  101  according to an example embodiment includes an electrode assembly  10  formed by winding a positive electrode (e.g., a first electrode)  11  and a negative electrode (e.g., a second electrode)  12  with a separator  13  interposed therebetween, a case  26  in which the electrode assembly  10  is accommodated (e.g., stored), and a cap assembly  30  combined to or mounted at an opening of the case  26 . 
         [0037]    The rechargeable battery  101  according to the present example embodiment is illustrated as a prism-shaped lithium ion rechargeable battery. 
         [0038]    However, the present invention is not limited thereto, and it can be applied to various types of batteries, such as a lithium polymer battery or variously shaped batteries, such as a cylindrical battery and the like. 
         [0039]    The positive electrode  11  and the negative electrode  12  each include coated regions where an active material is coated on a current collector formed of a thin metal foil and uncoated regions  11   a  and  12   a  where the active material is not coated thereon. 
         [0040]    The positive electrode uncoated region  11   a  is formed at one lateral end of the electrode assembly  10  along a length direction thereof, and the negative electrode uncoated region  12   a  is formed at the other lateral end of the electrode assembly  10  along the length direction thereof. 
         [0041]    The positive electrode  11  and the negative electrode  12  are wound together and the separator  13 , which operates as an insulator, is interposed between them. 
         [0042]    However, the present invention is not limited thereto, and the electrode assembly  10  may be formed having a layered structure in which the negative electrode and the positive electrode, respectively formed of a plurality of sheets, are layered while the separator is interposed between them. 
         [0043]    The case  26  may be roughly formed in a shape of a cuboid, and an opening may be formed at one side. 
         [0044]    The case  26  may be made of a metal, such as aluminum, stainless steel, or the like. 
         [0045]    The cap assembly  30  includes a cap plate  31  covering the opening of the case  26 , a first terminal  21  protruding out of the cap plate  31  and coupled to (e.g., electrically connected to) the positive electrode  11 , and a second terminal  22  protruding out of the cap plate  31  and coupled to (e.g., electrically connected to) the negative electrode  12 . 
         [0046]    The cap plate  31  may be formed in an elongated plate shape in one direction and is combined to the opening of the case  26 . 
         [0047]    The cap plate  31  includes a sealing cap  38  provided in an electrolyte injection opening  32  and a vent plate  39  which is provided in a vent opening  34  (e.g., a vent hole). The vent plate  39  is formed with a notch  39   a  set or configured to open at a reference pressure (e.g., a predetermined pressure). 
         [0048]    The first and second terminals  21  and  22  are provided to protrude upwards from the cap plate  31 . 
         [0049]    The first terminal  21  is coupled to (e.g., electrically connected to) the positive electrode  11  through a current collecting tab  41 , and the second terminal  22  may be coupled to (e.g., electrically connected to) the negative electrode  12  through a current collecting tab  42 . 
         [0050]    However, the present invention is not limited thereto, and the first terminal  21  may be coupled to the negative electrode  12 , while the second terminal  22  may be coupled to the positive electrode  11 . 
         [0051]    As shown in  FIG. 1  and  FIG. 2 , the first terminal  21  may be formed in a rectangular plate shape. 
         [0052]    The first terminal  21  is coupled to (e.g., electrically connected to) the positive electrode  11  through a connecting terminal  25  coupled to (e.g., bonded to) the current collecting tab  41 . 
         [0053]    The connecting terminal  25  coupled to (e.g., combined to) the first terminal  21  may have substantially the same structure as the connecting terminal  25  coupled to (e.g., combined to) the second terminal  22 . 
         [0054]    A gasket  59  for sealing is provided between the connecting terminal  25  and the cap plate  31  and is inserted into an opening (e.g., a hole) that the connecting terminal  25  penetrates, and a lower insulating member  45  is provided under the cap plate  31  to insulate the first terminal  21  from the current collecting tab  41  at the cap plate  31 . 
         [0055]    A connecting plate  58  coupling (e.g., electrically connecting) the first terminal  21  and the cap plate  31  is provided at the bottom side of the first terminal  21 . 
         [0056]    The connecting plate  58  is be penetrated by the connecting terminal  25  and is disposed between the cap plate  31  and the first terminal  21 . 
         [0057]    Having such a structure, the cap plate  31  may be coupled to (e.g., electrically connected to) the first electrode  21 . 
         [0058]    As shown in  FIG. 1 ,  FIG. 2 , and  FIG. 3 , the second terminal  22  may be formed in a rectangular plate shape. 
         [0059]    The second terminal  22  may be coupled to (e.g., electrically connected to) the negative electrode  12  through the connecting terminal  25  coupled to (e.g., bonded to) the current collecting tab  42 . 
         [0060]    The connecting terminal  25  includes a pillar portion  25   a  which penetrates the cap plate  31  and the second terminal  22  and has its upper part fixed to the second terminal  22 , a lower flange portion  25   b  which protrudes outwards from a lower end of the pillar portion  25   a , and a lower protrusion  25   c  protruding downwards from a lower end of the pillar portion  25   a , being inserted into the current collecting tab  42  and fixed thereto by, for example, welding. 
         [0061]    A gasket  55  for sealing is provided between the connecting terminal  25  and the cap plate  31  and is inserted into an opening (e.g., a hole) that the connecting terminal  25  penetrates, and a lower insulating member  43  may be provided under the cap plate  31  to insulate the first terminal  22  from the current collecting tab  42  at the cap plate  31 . 
         [0062]    Meanwhile, a short-circuit protrusion  22   c  protrudes towards a short-circuit opening  37  (e.g., a short-circuit hole) at the bottom side of the second terminal  22 . 
         [0063]    The second terminal  22  is elongated along one direction to cover the short-circuit opening  37 . 
         [0064]    An upper insulating member  54  is provided between the second terminal  22  and the cap plate  31  to electrically insulate them. 
         [0065]    Because the cap assembly  30  includes a short-circuit member  56  which short-circuits (e.g., electrically couples) the positive electrode  11  and the negative electrode  12 , the short-circuit member  56  is coupled to (e.g., electrically connected to) the cap plate  31  and is deformed (e.g., inverted) to contact (e.g., to be connected to) the second terminal  22  when internal pressure of the rechargeable battery  101  is increased (e.g., when internal pressure of the rechargeable battery  101  is increased above a predetermined level). 
         [0066]    The short-circuit opening  37  is formed in the cap plate  31 , and the short-circuit member  56  is disposed between the upper insulating member  54  and the cap plate  31  at the short-circuit opening  37 . 
         [0067]    The short-circuit member  56  includes a curved portion  56   a  which is convexly curved downwards in an arc shape and an edge portion  56   b  which is formed outside of (e.g., around) the curved portion  56   a  and fixed to the cap plate  31 . 
         [0068]    Having such a structure, the short-circuit member  56 , convexly curved downwards, may be deformed to be convexly curved upwards such that the short-circuit protrusion  22   c  contacts the short-circuit member  56  when internal pressure of the rechargeable battery  101  is increased. 
         [0069]    The upper insulating member  54  includes supporting protrusions  543  and  545  which are formed to protrude from respective lateral ends of the upper insulating member  54  along a length direction thereof. 
         [0070]    The upper insulating member  54  includes a lower plate formed in a rectangular plate shape and a side wall protruding from lateral ends of the lower plate. 
         [0071]    The supporting protrusions  543  and  545  may contact supporting steps  22   a  and  22   b  which are formed in the second terminal  22  and support the second terminal  22 . 
         [0072]    The supporting steps  22   a  and  22   b  are formed to be stepped from respective lateral ends of the second terminal  22  along a length direction thereof and are respectively coupled to (e.g., combined to) the supporting protrusions  543  and  545 . 
         [0073]    The supporting protrusions  543  and  545  are formed with a catching portion protruding towards the inside of the lower plate, the catching portion contacts top surfaces of the supporting steps  22   a  and  22   b  and supports the second terminal  22 . 
         [0074]    As shown in  FIG. 4 , the second terminal  22  is formed in a rectangular plate shape, and the short-circuit protrusion  22   c  protruding towards the short-circuit member  56  may be integrally formed with the second terminal  22  at a bottom side thereof. 
         [0075]    However, the present invention is no limited thereto, and the short-circuit protrusion  22   c  may be attached to the second terminal  22  by, for example, welding and the like. 
         [0076]    The second terminal  22  is formed with a terminal opening  22   d  (e.g., a terminal hole) and a supporting groove  22   e  into which a supporting protrusion formed in the cap plate is inserted. 
         [0077]    The short-circuit protrusion  22   c  is formed to protrude downwards from a bottom side of the second terminal  22  and is formed to be elongated in (e.g., protrude in) a circular ring shape. 
         [0078]    However, the present invention is no limited thereto, and the short-circuit protrusion  22   c  may be formed to protrude in various shapes. 
         [0079]    The surface roughness (R a ) of the short-circuit protrusion  22   c  is greater than that of the cap plate  31 . 
         [0080]    To achieve this, the surface of the second terminal  22  may be processed by various methods, for example, a sandblasting process, acid or base etching, stamping using a stamp with micro-sized protrusions, and the like. 
         [0081]    Accordingly, in the described embodiment, the short-circuit protrusion  22   c  is formed with micro-sized protrusions  22   f , and these micro-sized protrusions  22   f  may be formed over substantially the entire surface area of the second terminal  22  as all of the surface area is processed. 
         [0082]    The surface roughness (R a ) of the short-circuit protrusion  22   c  may be about 1.3 to about 10 times greater than that of the cap plate  31 . 
         [0083]    The average length of the micro-sized protrusions  22   f  producing the surface roughness (R a ) of the short-circuit protrusion  22   c  may be about 0.5 μm to about 100 μm. 
         [0084]    In the present example embodiment, as the surface roughness of the short-circuit protrusion  22   c  increases, the deformed short-circuit member  56  has a larger contact area when contacting the short-circuit protrusion  22   c.    
         [0085]    When the contact area between the short-circuit protrusion  22   c  and the short-circuit member  56  is small, the short-circuit member  56  may be more easily melted due to the contact resistance between the short-circuit protrusion  22   c  and the short-circuit member  56 , thereby stopping the short-circuit. 
         [0086]    However, according to the present example embodiment, because the short-circuit member  56  contacts the short-circuit protrusion  22   c  through the micro-sized protrusions  22   f , the contact resistance may be reduced as the number of contact points is increased.  FIG. 5A  is a photograph showing a part of the second terminal before the surface processing, and  FIG. 5B  is a photograph showing the part of the second terminal after the surface processing. 
         [0087]    As shown in  FIG. 5A , the second terminal  22  has a smooth surface before the surface processing, but the surface roughness is increased, as shown in  FIG. 5B , after surface processing by acid etching. 
         [0088]    Moreover, impurities on the surface of the second terminal  22  may be removed if the surface is processed by acid etching and organic materials such as oil, carbon, and the like may also be removed (e.g., completely removed). 
         [0089]    A sandblasting process is a process in which the surface of the second terminal  22  is processed by being sprayed with tiny materials such as sand and the like, which increases the surface roughness of the second terminal  22 . 
         [0090]    A stamping process is a process in which the short-circuit protrusion and the second terminal  22  are stamped with a stamp having micro-sized protrusions, which increases the surface roughness of the short-circuit protrusion  22   c.    
         [0091]      FIG. 6  is a perspective view of a second terminal according to a second example embodiment. 
         [0092]    Referring to  FIG. 6 , because a rechargeable battery according to the present example embodiment has substantially the same structure as the first example embodiment described above, except for a second terminal, a repeated description of the same structure will be omitted. 
         [0093]    The second terminal  70  according to the present example embodiment is formed in a rectangular plate shape, and a short-circuit protrusion  71  is formed to protrude towards the short-circuit member  56  from a bottom side of the second terminal  70 . 
         [0094]    The second terminal  70  is formed with a terminal opening  72  (e.g., a terminal hole) into which the connecting terminal is inserted, and a supporting groove  73  into which the supporting protrusion formed in the cap plate  31  is inserted. 
         [0095]    The short-circuit protrusion  71  protrudes downwards from a bottom side of the second terminal  70  and is elongated in (e.g., protrude in) a circular ring shape. 
         [0096]    However, the present invention is not limited thereto, and the short-circuit protrusion  71  may be formed in various suitable shapes. 
         [0097]    The surface roughness (R a ) of the short-circuit protrusion  71  may be greater than that of the cap plate  31 . 
         [0098]    The surface roughness (R a ) of the short-circuit protrusion  71  may be greater than that of the parts of the second terminal  70  other than the short-circuit protrusion  71 . 
         [0099]    That is, only the surface of the short-circuit protrusion  71  may be processed, and the surface of the second terminal  70  other than the short-circuit protrusion  71  may not be processed. 
         [0100]    To achieve this, the surface of the short-circuit protrusion  71  may be processed by various suitable methods, for example, a sandblasting process, acid or base etching, and stamping using a stamp with micro-sized protrusions, and/or the like. 
         [0101]    To achieve this, only the short-circuit protrusion  71  may be etched by an acid or base, and the short-circuit protrusion  71 , with its surface processed, may be coupled to (e.g., fixed to) the second terminal by, for example, welding. 
         [0102]    Accordingly, the short-circuit protrusion  71  may be formed with micro-sized protrusions  75 , and these micro-sized protrusions  75  may be formed only in the short-circuit protrusion  71  of the second terminal  70 . 
         [0103]    The surface roughness (R a ) of the short-circuit protrusion  71  may be about 1.3 to about 10 times greater than that of the other remaining parts of the second terminal  70  other than the short-circuit protrusion  71 . 
         [0104]    The average length of the micro-sized protrusions  75  producing the surface roughness (R a ) of the short-circuit protrusion  71  may be about 0.5 μm to about 100 μm. 
         [0105]    In the present example embodiment, as the surface roughness of the short-circuit protrusion  71  increases, the deformed short-circuit member  56  has a larger contact area when contacting the short-circuit protrusion  71 . 
         [0106]    Accordingly, contact resistance between the short-circuit member  56  and the short-circuit protrusion  71  may be reduced. 
         [0107]    While this disclosure has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 Description of Reference Symbols 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 101: rechargeable battery 
                 10: electrode assembly 
               
               
                 11: positive electrode 
                 11a: positive electrode uncoated region 
               
               
                 12: negative electrode 
                 12a: negative electrode uncoated region 
               
               
                 13: separator 
                 21: first terminal 
               
               
                 22, 70: second terminal 
                 22a, 22b: supporting step 
               
               
                 22c, 71: short-circuit protrusion 
                 22d, 72: terminal opening 
               
               
                 22e, 73: supporting groove 
                 22f, 75: micro-sized protrusion 
               
               
                 26: case 
                 30: cap assembly 
               
               
                 31: cap plate 
                 37: short-circuit opening 
               
               
                 54: upper insulating member 
                 543, 545: supporting protrusion 
               
               
                 55, 59: sealing gasket 
                 56: short-circuit member 
               
               
                 56a: curved portion 
                 56b: edge portion 
               
               
                 58: connecting plate