Abstract:
A rechargeable battery includes a case; an electrode assembly housed in the case and having a first substantially planar surface, a second substantially planar surface and a connecting portion connecting the substantially planar surfaces; and a support plate between the case and the electrode assembly, wherein the support plate is electrically coupled to the electrode assembly and has a substantially planar portion generally adjacent to and overlapping at least one of the substantially planar surfaces.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/267,354, filed on Dec. 7, 2009, in the United States Patent and Trademark Office, and claims priority to Korean Patent Application No. 10-2010-0042961, filed on May 7, 2010, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    This disclosure relates to a rechargeable battery and more particularly to a rechargeable battery including a safety device. 
         [0004]    2. Description of the Related Art 
         [0005]    A rechargeable battery can be recharged and discharged unlike a primary battery that cannot be recharged. A rechargeable battery with low capacity is often used for a small portable electronic device such as a mobile phone, a laptop computer, and a camcorder, while a rechargeable battery with large capacity is typically used as a power source for driving a motor such as for a hybrid vehicle. 
         [0006]    Recently, a large capacity high power rechargeable battery has been developed using a non-aqueous electrolyte with high energy density. The aforementioned rechargeable battery with large capacity is formed into a battery module with large capacity by coupling a plurality of these rechargeable batteries in series or in parallel in order to use them to drive a device, for example, a motor in an electric vehicle requiring a large amount of electric power. The rechargeable battery may be fabricated to have a cylindrical shape, a prismatic shape, and the like. 
         [0007]    A prismatic rechargeable battery includes an electrode assembly including positive and negative electrodes and a separator therebetween, a case having a space in which the electrode assembly is located, a cap plate closing and sealing the case, and a terminal electrically connected to the electrode assembly and protruding through the cap plate out of the case. 
         [0008]    If the rechargeable battery is pierced by a conductive foreign particle such as a nail, a drill, or the like, a short circuit may occur inside the battery. The short circuit may sharply increase a temperature inside the rechargeable battery and cause danger of a spark or explosion. 
         [0009]    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 
       [0010]    An exemplary embodiment of the present invention provides a rechargeable having improved safety. 
         [0011]    According to one embodiment of the present invention, a rechargeable battery is provided including a case; an electrode assembly housed in the case and having a first substantially planar surface, a second substantially planar surface and a connecting portion connecting the substantially planar surfaces; and a support plate between the case and the electrode assembly, wherein the support plate is electrically coupled to the electrode assembly and has a substantially planar portion generally adjacent to and overlapping at least one of the substantially planar surfaces. 
         [0012]    In one embodiment, an insulating film is between the support plate and the electrode assembly. Additionally, the electrode assembly may include a first electrode, a second electrode and a separator between the first electrode and the second electrode, wherein the first electrode has a coated region coated with an active material and an uncoated region absent the active material and wherein the support plate is electrically coupled to the first electrode at the uncoated region. 
         [0013]    In one embodiment, the support plate has an angled surface generally corresponding to an angled region of the first electrode, and an attachment surface generally corresponding to the uncoated region of the first electrode. In one embodiment, the support plate and the first electrode comprise the same material and in another embodiment the second electrode and the case comprise the same material. 
         [0014]    In one embodiment, the electrode assembly has a second substantially planar surface and wherein the rechargeable battery further comprises a second support plate between the case and the second substantially planar surface of the electrode assembly wherein the second support plate is electrically coupled to the electrode assembly and has a substantially planar portion generally overlapping the second substantially planar surface. In one embodiment, the support plate does not cover the connecting portion of the electrode assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  provides the perspective view of a rechargeable battery according to a first embodiment of the present invention. 
           [0016]      FIG. 2  is the cross-sectional view of a rechargeable battery cut along the II-II line in  FIG. 1 . 
           [0017]      FIG. 3  is an exploded perspective view showing an electrode assembly and a metal supporting plate according to the first embodiment of the present invention. 
           [0018]      FIG. 4  is the horizontally cross-sectional view of members illustrated in  FIG. 3 , when combined. 
           [0019]      FIG. 5  is a horizontally cross-sectional view showing a metal-supporting plate attached to an electrode assembly according to a second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF REFERENCE NUMERALS INDICATING PRIMARY ELEMENTS IN THE DRAWINGS 
       [0020]      
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 100: rechargeable battery 
                 10: electrode assembly 
               
               
                 11: positive electrode 
                 12: negative electrode 
               
               
                 11a: positive uncoated region 
                 12a: negative uncoated region 
               
               
                 13: separator 
                 20: cap assembly 
               
               
                 21: positive terminal 
                 22: negative terminal 
               
               
                 21a, 22a: terminal flange 
                 24: washer 
               
               
                 25: gasket 
                 26: insulating member 
               
               
                 27: electrolyte injection opening 
                 29: nut 
               
               
                 30: cap plate 
                 32: lead member 
               
               
                 34: case 
                 38: sealing cover 
               
               
                 39: vent member 
                 39a: notch 
               
               
                 40: metal supporting plate 
                 41, 61, 71: flat part 
               
               
                 42, 62, 63: curving slope part 
                 43, 63, 73: junction part 
               
               
                 45, 65, 75: insulating film 
                 60: first metal supporting plate 
               
               
                 70: second metal supporting plate 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION 
       [0021]    This disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of this disclosure are shown. As those skilled in the art would realize, the described embodiments may be modified in various ways all without departing from the spirit or scope of this disclosure. In the specification and drawings, like reference numerals designate like elements. 
         [0022]      FIG. 1  is the perspective view of a rechargeable battery according to the first embodiment, while  FIG. 2  is a cross-sectional view of the rechargeable battery cut along the line II-II. 
         [0023]    Referring to  FIGS. 1 and 2 , a rechargeable battery  100  according to a first embodiment of the present invention includes an electrode assembly  10  fabricated by winding positive and negative electrodes  11  and  12  and a separator  13  located therebetween, a case housing the electrode assembly  10 , and a cap assembly  20  combined with the case  34 . 
         [0024]    According to the first embodiment of the present invention, a rechargeable battery  100  will be illustrated as a prismatic lithium ion secondary battery. However, this disclosure of embodiments of the present invention is not limited thereto, but rather may be applied to various battery types such as a lithium polymer battery, a cylindrical battery, or the like. 
         [0025]    The positive and negative electrodes  11  and  12  may include a coating region prepared by coating a current collector made of a thin metal foil plate with an active material and uncoated regions  11   a  and  12   a  not coated with the active material. 
         [0026]    The positive uncoated region  11   a  is formed at one end of the positive electrode  11  along the length direction, while the negative uncoated region  12   a  is formed at the other end of the negative electrode  12  along the length direction. Next, the positive and negative electrodes  11  and  12  and the separator  13  therebetween as an insulator are spiral-wound. In addition, the electrode assembly  10  may be supported outside by a finishing tape to support the shape. 
         [0027]    However, this disclosure is not limited thereto but may include the electrode assembly  10  prepared by laminating a plurality of positive and negative electrodes and a separator therebetween. 
         [0028]    The case  34  has a generally cuboid shape and an opening at one side. The cap assembly  20  includes a cap plate  30  covering the opening of the case  34 , a positive terminal  21  protruding from the cap plate  30  and electrically connected to the positive electrode  11 , a negative terminal  22  protruding from the cap plate  30  and electrically connected to the negative electrode, and a vent member  39  equipped with a notch  39   a  that can be fractured depending on a predetermined internal pressure. 
         [0029]    The cap plate  30  is made of a thin plate and includes an electrolyte injection opening  27  for implanting an electrolyte solution at one side and a sealing cover  38  for sealing the electrolyte injection opening  27 . 
         [0030]    Between the cap plate  30  and terminals  21  and  22  is a gasket  25  to electrically insulate the cap plate  30  from the terminals  21  and  22 . The terminals  21  and  22  include a positive terminal  21  and a negative terminal  22 . The gasket  25  is fit into the terminal hole. In one embodiment, the gasket  25  is made of two pieces and respectively positioned adjacent to top and bottom of the terminal hole. 
         [0031]    The terminals  21  and  22  have a generally circular cylinder shape and a screw thread on the external circumference for attachment of a nut. They may further include a washer  24  between the nut  29  and the gasket  25  to buffer their combining strength. Additionally, the terminals  21  and  22  have terminal flanges  21   a  and  22   a  at the bottom to support themselves. 
         [0032]    Between the terminal flanges  21   a  and  22   a  and the cap plate  30  is a lower insulating member  26  for insulation. The terminals  21  and  22  are inserted into the lower insulating member  26 . The terminal flanges  21   a  and  22   a  are welded with a lead member  32  electrically connected to a positive electrode  11  or negative electrode  12 . The terminal flanges  21   a  and  22   a  and the lead member  32  are fit into a hole formed at the bottom of the lower insulating member  26 . 
         [0033]    In addition, a metal supporting plate  40  is welded into the negative uncoated region  12   a  to externally support the electrode assembly  10 . 
         [0034]      FIG. 3  is an exploded perspective view of an electrode assembly and a metal supporting plate according to the first embodiment of the present invention.  FIG. 4  is a horizontally cross-sectional view of the above members shown in  FIG. 3  when combined. 
         [0035]    Referring to  FIGS. 3 and 4 , the metal supporting plate  40  according to the first embodiment of the present invention includes a flat part or substantially planar portion  41  facing the front side of the electrode assembly  10 , a curving slope part or angled region  42  formed at one end of the flat part  41  and curved or angled toward an electrode assembly, and a junction part or attachment surface  43  formed at the end of the curving slope part  42  and electrically connected to the negative uncoated region  12   a.    
         [0036]    The metal supporting plate  40  is welded with the negative uncoated region  12   a  at the junction part  43  and is made of the same material as the negative uncoated region  12   a . According to an embodiment of the present, the metal supporting plate  40  is made of copper or a copper alloy. 
         [0037]    An insulating film  45  is located between the flat part  41  and the electrode assembly. The insulating film  45  is attached to the flat part  41  and, by being made of a polymer material that does not react with an electrolyte solution, it prevents the electrode assembly  10  from being electrically connected to the flat part  41 . 
         [0038]    Since uncoated regions  11   a  and  12   a  of the electrode assembly  10  are thinner than the coated regions, they are formed to be tilted at an angle where the uncoated regions  11   a  and  12   a  meet coated regions coated with an active material. The uncoated regions  11   a  and  12   a  are welded together in order to efficiently withdraw a current accumulated therein with low resistances. 
         [0039]    The curving slope part  42  in the metal supporting plate  40  contacts the angled negative uncoated region  12   a  and supports it. The junction part  43  is adjacent the electrode assembly  10  due to the curving slope part  42  generally following a contour of the electrode assembly and can be easily welded to the negative uncoated region  12   a . The junction part  43  is oriented in parallel to the negative uncoated region  12   a  and welded to the negative uncoated region  12   a . Accordingly, it can substantially prevent the negative uncoated region  12   a  from being shaken or dislodged due to external impact or vibration. 
         [0040]    Since the negative uncoated region  12   a  is welded with a lead member  32 , there may be insufficient contact between the negative uncoated region  12   a  and the lead member  32  if the negative uncoated region  12   a  is shaken or dislodged due to external impact or vibration. However, when the junction part  43  supports the negative uncoated region  12   a  as in an embodiment of the present invention, insufficient contact between the uncoated region  12   a  and the lead member  32  due to external impact, vibration, or the like may be substantially prevented. 
         [0041]    When a rechargeable battery  100  is pierced by a conductive foreign particle such as a nail, a drill, or the like, the metal supporting plate  40  may be short-circuited to the positive electrode  11 , discharging an accumulated current. In a Comparative Example, a metal supporting plate was attached to a positive uncoated region and tested to see if the positive uncoated region was short-circuited to a negative electrode. As a result of the test, the electrode assembly caught fire due to abrupt heat where the supporting plate electrically connected to a positive electrode contacted the negative electrode. In addition, when a metal supporting plate was not included, as tested, in another Comparative Example, positive and negative electrodes were short-circuited and generated much heat, causing an electrode assembly  10  to catch fire when a rechargeable battery was externally pierced by a nail, a drill, and the like. 
         [0042]    However, when a metal supporting plate  40  is connected to a negative electrode  12  according to an embodiment of the present invention and is short-circuited to a positive electrode  11  due to a nail piercing a rechargeable battery  100  inside an electrode assembly  10 , a current accumulated inside the electrode assembly  10  may be safely discharged without causing the electrode assembly to catch fire. The positive electrode  11  may be configured to connect electrically to the case  34 , and thus the metal supporting plate  40  connected to the negative electrode  12  can be short-circuited to the case  34  connected to the positive electrode  11 . 
         [0043]    In this way, according to one embodiment of the present invention, a rechargeable battery  100  can improve safety by discharging a current and thus, removing a danger of fire when there is a possibility of an explosion when the battery  100  is externally pierced by a foreign particle. 
         [0044]      FIG. 5  is a horizontally cross-sectional view of a metal supporting plate attached to an electrode assembly according to a second embodiment of the present invention. 
         [0045]    Referring to  FIG. 5 , a rechargeable battery according to an embodiment of the present invention includes a first metal supporting plate  60  attached to one side of the electrode assembly  10  and a second metal supporting plate  70  attached to the other side thereof. 
         [0046]    According to an embodiment of the present invention, the electrode assembly  10  has the same structure as the first embodiment and thus, the description will not be repetitively illustrated here. 
         [0047]    The first metal supporting plate  60  includes a flat part  61  facing one side of the electrode assembly  10 , a curving or angled slope part  62  connected to one end of the flat part  61  and curved or angled toward the electrode assembly  10 , and a junction part  63  protruding from the curving slope part  62 . The flat part  61  may have a quadrilateral shape. In one embodiment, an insulating film  65  is located between the flat part  61  and the electrode assembly  10 . The insulating film  65  may be made of a polymer material and attached to the flat part  61 . 
         [0048]    In addition, a second metal supporting plate  70  includes a flat part  71  facing the other side of the electrode assembly  10 , a curved or angled slope part  72  connected to one end of the flat part  71  and curved or angled toward the electrode assembly  10 , and a junction part  73  protruding from one end of the curved slope part  72 . The flat part  71  may have a quadrilateral shape. In one embodiment, an insulating film  75  is located between the flat part  71  and the electrode assembly  10 . The insulating film  75  may be made of a polymer material and attached to the flat part  71 . 
         [0049]    The junction part  63  of the first metal supporting plate  60  and the junction part  73  of the second metal supporting plate  70  are welded to a negative uncoated region  12   a  and thus, electrically connected to a negative electrode  12 . 
         [0050]    The first and second metal supporting plates  60  and  70  are made of the same material as a negative electrode current collector and in particular, copper or a copper alloy. 
         [0051]    According to an embodiment of the present invention, when the metal supporting plates  60  and  70  are located on both sides of the electrode assembly  10 , a rechargeable battery may be safer because a current inside an electrode assembly  10  may be discharged without causing fire or an explosion even when the rechargeable battery is pierced by a drill or a similar implement. 
         [0052]    While this disclosure has been described in connection with what is presently considered to be practical exemplary 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.