Abstract:
A rechargeable battery includes a wound electrode assembly comprising a separator between a first electrode and a second electrode, wherein the first and second electrodes each include uncoated regions and coated regions; a case accommodating the electrode assembly; and a first electrode terminal and a second electrode terminal respectively coupled to the first and second electrodes and extending from the case, wherein an uncoated region of the first electrode includes inner and outer uncoated regions of a terminal end portion located at an outermost side of the electrode assembly, and wherein the second electrode includes an outer uncoated region of a terminal end portion facing the inner uncoated region of the first electrode and an additional inner coated region at an opposite side of the outer uncoated region.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2014-0152320 filed in the Korean Intellectual Property Office on Nov. 4, 2014, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a rechargeable battery. 
         [0004]    2. Description of the Related Art 
         [0005]    With advancement of technology for mobile devices, demand for rechargeable batteries as energy sources has been increasing. 
         [0006]    A rechargeable battery differs from a primary battery in that it can be repeatedly charged and discharged, while the latter is incapable of being recharged. 
         [0007]    A low-capacity rechargeable battery is used in small portable electronic devices such as mobile phones, notebook computers, and camcorders, while a high-capacity rechargeable battery can be used as a power source for driving motors of a hybrid vehicle, an electric vehicle, and the like. 
         [0008]    For example, a rechargeable battery may include an electrode assembly for performing charging and discharging operations, a case (or pouch) for accommodating the electrode assembly, and electrode tabs through which the electrode assembly is drawn out of the cap plate. 
         [0009]    As the trend of increasingly high-capacity rechargeable batteries continues, energy density increases and safety deteriorates as well. 
         [0010]    In order to improve this, sometimes uncoated regions are provided to be elongated at terminal end portions of the positive and negative electrodes, thereby causing an initial short-circuit between a positive electrode member and a negative electrode member when a conductive member penetrates. 
         [0011]    Accordingly, when heat is generated due to a high current, the elongated uncoated regions serve to prevent other members, for example, a separator, from catching fire. 
         [0012]    The additional uncoated regions of the positive and negative electrode members and a resultant additional portion of the separator decrease internal volume of the rechargeable battery while not affecting battery capacity. 
         [0013]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention 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 
       [0014]    One aspect of the present invention provides a rechargeable battery for enabling increased battery capacity and improved safety. 
         [0015]    A rechargeable battery according to an exemplary embodiment of the present invention includes: an electrode assembly spirally wound by interposing a separator between a first electrode and a second electrode that include uncoated regions and coated regions; a case for accommodating the electrode assembly; and a first electrode terminal and a second electrode terminal coupled to the first and second electrodes to be drawn out of the case. An uncoated region of the first electrode includes inner and outer uncoated regions of a terminal end portion that is disposed at an outermost side of the electrode assembly, and the second electrode includes an outer uncoated region of a terminal end portion facing the inner uncoated region of the first electrode and an additional inner coated region at an opposite side of the outer uncoated region. 
         [0016]    In the terminal end portion, the inner uncoated region of the first electrode may have a first length L 1  corresponding to a width W of the electrode assembly, and the outer uncoated region of the first electrode may have a second length L 2  corresponding to one winding range of the outermost side of the electrode assembly. 
         [0017]    The outer uncoated region of the second electrode may have a third length L 3  that is greater than a width W of the electrode assembly or set to two-thirds thereof. 
         [0018]    The additional inner coated region may be formed at the opposite side of the outer uncoated region of the second electrode to have the same length as the third length. 
         [0019]    The additional inner coated region may include one portion that is formed to have a thickness which is greater than a thickness of the inner coated region that is formed at an inner side of the second electrode. 
         [0020]    The first electrode may further include double-sided uncoated regions of a front end portion that is disposed at a center of the electrode assembly, the second electrode may include inner and outer uncoated regions of the front end portion in the front end portion that is disposed at the center of the electrode assembly, the second electrode terminal may be coupled to the inner uncoated region of the front end portion, and an additional outer coated region may be provided at an opposite side of the inner uncoated region of the front end portion. 
         [0021]    The additional outer coated region may be formed to have the same thickness as that of the outer coated region that is formed at an outer side of the second electrode. 
         [0022]    The second electrode may include an additional inner coated region that is formed at an opposite side of the outer uncoated region in the terminal end portion of the electrode assembly, and an additional outer coated region that is formed at an opposite side of the inner uncoated region of the front end portion in the front end portion of the electrode assembly. 
         [0023]    The uncoated region of the first electrode may further include double-sided uncoated regions corresponding to the outer uncoated region of the second electrode in the front end portion of the electrode assembly, and the coated region of the first electrode includes double-sided coated regions corresponding to the additional outer coated region. 
         [0024]    As described above, in the exemplary embodiment of the present invention, the battery capacity can be increased since the additional inner coated region is provided at the opposite side of the outer uncoated region of the second electrode to face the coated region of the first electrode, and an initial short-circuit is caused to improve safety when the conductive member penetrates since the outer uncoated region of the second electrode faces the inner uncoated region of the first electrode. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is an exploded perspective view of a rechargeable battery according to an exemplary embodiment of the present invention. 
           [0026]      FIG. 2  is a perspective view of the rechargeable battery of  FIG. 1 . 
           [0027]      FIG. 3  is an enlarged cross-sectional view of an electrode assembly applicable to  FIG. 1 . 
           [0028]      FIG. 4  is a cross-sectional view of a front end portion and a terminal end portion of a positive electrode and a negative electrode applicable to the electrode assembly of  FIG. 3  when they are unfolded. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0030]    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. 
         [0031]    The drawings and description are to be regarded as illustrative in nature and not restrictive, and like reference numerals designate like elements throughout the specification. 
         [0032]      FIG. 1  is an exploded perspective view of a rechargeable battery according to an exemplary embodiment of the present invention, and  FIG. 2  is a perspective view of the rechargeable battery of  FIG. 1 . 
         [0033]    Referring to  FIGS. 1 and 2 , the rechargeable battery includes an electrode assembly  110 , and a case (hereinafter referred to as “pouch  120 ”) for accommodating the electrode assembly  110 . 
         [0034]    The electrode assembly  110  is formed in a jelly-roll form by providing a first electrode  11  (for convenience, referred to as a “positive electrode”) and a second electrode  12  (for convenience, referred to as a “negative electrode”) with a separator  13  therebetween. 
         [0035]    The separator  13  may be formed of a polymer film through which lithium ions can pass. 
         [0036]    The electrode assembly  110  further includes a first electrode terminal  14  (for convenience, referred to as a “positive electrode terminal”) and a second electrode terminal  15  (for convenience, referred to as a “negative electrode terminal”) that are respectively coupled to the positive and negative electrodes  11  and  12 . 
         [0037]      FIG. 3  is an enlarged cross-sectional view of the electrode assembly applicable to  FIG. 1 , and  FIG. 4  is a cross-sectional view of a front end portion and a terminal end portion of the positive electrode and the negative electrode applicable to the electrode assembly of  FIG. 3  when they are unfolded. 
         [0038]    Referring to  FIGS. 3 and 4 , the positive electrode  11  includes a coated region  11   a  where an active material is coated on a current collector made of a thin metal plate (an inner coated region  111   a  and an outer coated region  112   a ), and an uncoated region  11   b  that is formed as an exposed current collector because an active material is not coated thereon. 
         [0039]    For example, the current collector of the positive electrode  11  and the positive electrode terminal  14  may be formed of aluminum (Al). 
         [0040]    The negative electrode  12  includes a coated region  12   a  where an active material different from the active material of the positive electrode  11  is coated on a current collector made of a thin metal plate (an inner coated region  121   a  and an outer coated region  122   a ), and an uncoated region  12   b  that is formed as an exposed current collector because an active material is not coated thereon. 
         [0041]    For example, the current collector of the negative electrode  12  and the negative terminal  15  may be formed of copper (Cu). 
         [0042]    The positive electrode terminal  14  is coupled to the uncoated region  11   b  of the positive electrode  11 , and the negative electrode terminal  15  is coupled to the uncoated region  12   b  of the negative electrode  12  while being spaced from the positive electrode terminal  14 . 
         [0043]    The positive and negative electrode terminals  14  and  15  separately extend from the same lateral side of the electrode assembly  10  (to the left of  FIGS. 1 and 2 ). 
         [0044]    Though not illustrated, the positive and negative terminals may be located at different lateral sides of the electrode assembly (for example, to the left and right of  FIGS. 1 and 2 ). 
         [0045]    Referring back to  FIGS. 1 and 2 , the pouch  120  accommodates the electrode assembly  110 , and an outer portion of the electrode assembly  110  is thermo-bonded to form the rechargeable battery. 
         [0046]    In one embodiment, the positive and negative electrode terminals  14  and  15  are coated with insulating members  16  and  17  to extend from the pouch  120  through the thermo-bonded portion. 
         [0047]    In other words, the insulating members  16  and  17  electrically insulate the positive electrode terminal  14  from the negative electrode terminal  15 , and electrically insulate the positive and negative electrode terminals  14  and  15  from the pouch  120 . 
         [0048]    The pouch  120  may be formed to have a multi-layered sheet structure that encloses an exterior of the electrode assembly  110 . 
         [0049]    In one embodiment, the pouch  120  includes a polymer sheet  121  that forms an inner side and performs insulating and thermo-bonding functions, a PET (polyethylene terephthalate) sheet that forms an outer side and performs a protecting function, a nylon sheet or a PET-nylon composite sheet  122  (for convenience, a “nylon sheet” will be exemplarily described), and a metal sheet  123  that provides mechanical strength. 
         [0050]    The metal sheet  123  is interposed between the polymer sheet  121  and the nylon sheet  122 , and may be formed of, for example, an aluminum sheet. 
         [0051]    The pouch  120  includes a first exterior member  201  that accommodates the electrode assembly  110 , and a second exterior member  202  that is thermo-bonded to the first exterior member  201  outside of the electrode assembly  110  while covering the electrode assembly  110 . 
         [0052]    The first and second exterior members  201  and  202  may be formed to have the same structure in which the polymer sheet  121 , the nylon sheet  122 , and the metal sheet  123  are layered. 
         [0053]    For example, the first exterior member  201  is formed to have a concave shape for accommodating the electrode assembly  110 , and the second exterior member  202  is formed to have a flat shape for covering the electrode assembly  110  accommodated in the first exterior member  201 . 
         [0054]    In one embodiment, the second exterior member may be coupled to the first exterior member. 
         [0055]    Referring back to  FIGS. 3 and 4 , the uncoated region  11   b  of the positive electrode  11  includes inner and outer uncoated regions  111   b  and  112   b  in a terminal end portion that is located at an outermost side of the electrode assembly  110 . 
         [0056]    In the terminal end portion of the electrode assembly  110 , the inner uncoated region  111   b  of the positive electrode  11  has a first length L 1  corresponding to a width W (L 1 =W) of the electrode assembly  110 . 
         [0057]    The outer uncoated region  112   b  of the positive electrode  11  has a second length L 2  corresponding to one winding range of the outermost side of the electrode assembly  110 . 
         [0058]    The outer uncoated region  112   b  prevents unnecessary waste of a material for the coated region  11   b  of the positive electrode  11  since it does not face the coated region  12   a  of the negative electrode  12 . 
         [0059]    The negative electrode  12  includes an outer uncoated region  121   b  of the terminal end portion that faces the inner uncoated region  111   b  of the positive electrode  11 , and an additional inner coated region  123   a  at an opposite side of the outer uncoated region  121   b.    
         [0060]    The outer uncoated region  121   b  of the negative electrode  12  may have a third length L 3  that is greater than the width W of the electrode assembly  110  or set to about two-thirds thereof. 
         [0061]    The outer uncoated region  121   b  of the negative electrode  12  faces the inner uncoated region  111   b  of the positive electrode  11  to cause a short-circuit at the outermost side of the electrode assembly  110  when a conductive member N penetrates, thereby improving safety of the rechargeable battery. 
         [0062]    The additional inner coated region  123   a  of the negative electrode  12  is formed at the opposite side of the outer uncoated region  121   b  of the negative electrode  12  to have the same length as the third length L 3 . 
         [0063]    The additional inner coated region  123   a  faces the outer coated region  112   a  of the positive electrode  12  in the electrode assembly  110 , thereby increasing capacity of the rechargeable battery. 
         [0064]    The additional inner coated region  123   a  includes one portion P that is formed to have a thickness t 2  which is greater than a thickness t 1  of the inner coated region  121   a  that is formed at an inner side of the negative electrode  12 . 
         [0065]    The additional inner coated region  123   a  may receive more lithium ions moving from the positive electrode  11  to the negative electrode  12  in the terminal end portion of the electrode assembly  110 . 
         [0066]    Accordingly, lithium is not deposited in the current collector of the negative electrode  12  that corresponds to the additional inner coated region  123   a.    
         [0067]    In other words, compared with an electrode assembly that is not provided with the additional inner coated region, the electrode assembly  110  of the present invention may have higher stability. 
         [0068]    In one embodiment, in the front end portion disposed at a center of the electrode assembly  110 , the positive electrode  11  further includes double-sided uncoated regions  113   b  and  114   b.    
         [0069]    In the front end portion located at the center of the electrode assembly  110 , the negative electrode  12  includes an inner uncoated region  122   b  of the front end portion and an outer uncoated region  123   b  of the front end portion. 
         [0070]    The negative electrode terminal  15  is coupled to the inner uncoated region  122   b  of the front end portion by welding, and includes an additional outer coated region  124   a  at an opposite side of the inner uncoated region  122   b  of the front end portion. 
         [0071]    The coated region  11   a  of the positive electrode  11  includes double-sided coated regions  113   a  and  114   a  corresponding to the additional outer coated region  124   a.    
         [0072]    The additional outer coated region  124   a  faces the inner coated region  113   a  of the double-sided coated regions  113   a  and  114   a  of the positive electrode  11 , thereby increasing the capacity of the rechargeable battery. 
         [0073]    The additional outer coated region  124   a  is formed to have the same thickness as the thickness t 3  of the outer coated region  122   a  that is formed at the outer side of the negative electrode  12 . 
         [0074]    Accordingly, when the same area is compared, the additional outer coated region  124   a  of the negative electrode  12  and the inner coated region  113   a  of the positive electrode  11  may have the same capacity as the outer coated region  122   a  of the negative electrode  12  and the inner coated region  111   a  of the positive electrode  11 . 
         [0075]    In other words, in the negative electrode  12 , the additional inner coated region  123   a  is formed at the opposite side of the outer uncoated region  121   b  in the terminal end portion of the electrode assembly  110 , while the additional outer coated region  124   a  is formed at the opposite side of the inner uncoated region  122   b  of the front end portion in the front end portion of the electrode assembly  110 . 
         [0076]    Thus, the additional inner coated region  123   a  of the negative electrode  12  and the additional outer coated region  124   a  further face the coated region  11   a  of the positive electrode  11 , thereby increasing capacity of the rechargeable battery and improving stability thereof. 
         [0077]    The uncoated region  11   b  of the positive electrode  11  further includes the double-sided uncoated regions  113   b  and  114   b  corresponding to the outer uncoated region  123   b  of the negative electrode  12  in the front end portion of the electrode assembly  110 . 
         [0078]    The double-sided uncoated regions  113   b  and  114   b  can minimize capacity degradation of the rechargeable battery since they are minimally formed due to the double-sided coated regions  113   a  and  114   a.    
         [0079]    In the exemplary embodiment of the present invention, a pouch type of rechargeable battery is illustrated, but it may also be applicable to cylindrical and prismatic rechargeable batteries. 
         [0080]    While this invention 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. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 Description of Symbols 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 11: first electrode (positive electrode) 
                 11a, 12a: coated region 
               
               
                 11b, 12b: uncoated region 
                 12: second electrode (negative 
               
               
                   
                 electrode) 
               
               
                 13: separator 
                 14: first electrode terminal 
               
               
                   
                 (positive electrode terminal) 
               
               
                 15: second electrode terminal 
               
               
                 (negative electrode terminal) 
               
               
                 16, 17: insulating member 
               
               
                 110: electrode assembly 
                 111a, 121a: inner coated region 
               
               
                 111b: inner uncoated region 
                 112a, 122a: outer coated region 
               
               
                 112b, 121b: outer uncoated region 
               
               
                 113a, 114a: double-sided (inner and 
               
               
                 outer side) coated region 
               
               
                 113b, 114b: double-sided uncoated 
                 120: case (pouch) 
               
               
                 region 
               
               
                 121: polymer sheet 
                 122: nylon sheet 
               
               
                 122b: inner uncoated region of front 
               
               
                 end portion 
               
               
                 123a: additional inner coated region 
               
               
                 123b: outer uncoated region of front 
                 123: metal sheet 
               
               
                 end portion 
               
               
                 124a: additional outer coated region 
                 201: first exterior member 
               
               
                 202: second exterior member 
                 L1, L2, L3: first, second, third 
               
               
                   
                 length 
               
               
                 t1, t2, t3: thickness 
                 W: width of electrode assembly