Abstract:
Provided are a lithium polymer battery and a method of manufacturing the lithium polymer battery. The lithium polymer battery comprises: an electrode assembly comprising a positive electrode, a negative electrode and a separator; a pouch enclosing the electrode assembly, the pouch comprising a first panel and a second panel generally opposing the first panel, the first panel comprising a first main surface, the second panel comprising a second main surface opposing the first main surface, the pouch further comprising a first step formed in the first panel in a perimeter thereof and stepped from the first main surface toward the second main surface, the first step comprising a first step surface generally parallel to the first main surface; and an insulation tape placed on the first step surface and comprising a first tape surface over the first step surface and facing away from the first step surface, wherein the first main surface is generally planar throughout, and the insulation tape is not placed over the first main surface, and wherein the first step and the insulation tape are sized such that the first tape surface is at a level not substantially higher than the first main surface

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/446,413, filed on Feb. 24, 2011, with the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments relate to a lithium polymer battery and a method of manufacturing the lithium polymer battery. 
         [0004]    2. Description of the Related Technology 
         [0005]    In a lithium polymer battery, a separator is typically disposed between positive and negative electrode plates as an ion transfer medium (that is, electrolyte) and a separating member, for example, in a lithium ion battery (hereinafter, an assembly of a positive electrode plate, a negative electrode plate, and a separator will be referred to as an “electrode assembly”). Such a separator is typically &amp;limed of a gel-type polymer electrolyte. For example, a separator may be formed by impregnating a polymer with electrolyte to improve ion conductivity. 
         [0006]    A lithium polymer battery may include a flexible pouch shape. In such a pouch type battery, an electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode may be disposed in a pouch, or an electrode assembly formed by stacking and winding a positive electrode, a separator, and a negative electrode may be disposed in a pouch. Edges of upper and lower films of the pouch are typically thermally bonded. The pouch is generally formed of a multilayer film including a metal foil layer and a synthetic resin layer (polymer layer) covering the metal foil layer. The metal foil layer is generally formed of aluminum. The polymer layer forming an inner layer of the pouch can protect the metal foil layer from electrolyte. The polymer film can also prevent a short circuit among the positive electrode, the negative electrode, and electrode tabs. If edges of the pouch are not insulated, the metal foil layer (middle layer) of the pouch may be exposed. In this case, a short circuit may occur between the exposed metal foil layer and a conductor of an external device. 
       SUMMARY 
       [0007]    An aspect of the present invention provides a lithium polymer battery comprising: an electrode assembly comprising a positive electrode, a negative electrode and a separator; a pouch enclosing the electrode assembly, the pouch comprising a first panel and a second panel generally opposing the first panel, the first panel comprising a first main surface, the second panel comprising a second main surface opposing the first main surface, the pouch further comprising a first step formed in the first panel in a perimeter thereof and stepped from the first main surface toward the second main surface, the first step comprising a first step surface generally parallel to the first main surface; and an insulation tape placed on the first step surface and comprising a first tape surface over the first step surface and facing away from the first step surface, wherein the first main surface is generally planar throughout, and the insulation tape is not placed over the first main surface, wherein the first step and the insulation tape are sized such that the first tape surface is at a level not substantially higher than the first main surface. 
         [0008]    A method of making a battery, the method comprising: providing a pouch for enclosing an electrode assembly, the pouch comprising a first panel and a second panel generally opposing the first panel; forming a first step in the first panel to provide a first main surface and a first step surface stepped toward the second panel, wherein the first main surface is substantially planar throughout; and placing an insulation tape on the first step surface such that the insulation tape has a first tape surface facing away from the first step surface, wherein the insulation tape is not placed over the first main surface, wherein the first step and the insulation tape are sized such that the first tape surface is at a level not substantially higher the first main surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view illustrating a lithium polymer battery according to an embodiment; 
           [0010]      FIG. 2  is a sectional view of the lithium polymer battery taken along line I-I′ of  FIG. 1 ; 
           [0011]      FIG. 3  is an enlarged sectional view illustrating portion (3) of  FIG. 2 ; 
           [0012]      FIG. 4  is a perspective view illustrating a sealed outer member of the lithium polymer battery illustrated in  FIG. 1 ; 
           [0013]      FIG. 5  is a perspective view illustrating a folded state of remaining parts of the sealed outer member of the lithium polymer battery illustrated in  FIG. 4 ; 
           [0014]      FIG. 6  is a flowchart for explaining a method of manufacturing a lithium polymer battery according to an embodiment; 
           [0015]      FIG. 7  is a sectional view illustrating a lithium polymer battery according to another embodiment,  FIG. 7  corresponding to  FIG. 2 ; and 
           [0016]      FIG. 8  is an enlarged sectional view illustrating portion (8) of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Hereinafter, a lithium polymer battery and a method of manufacturing the lithium polymer battery will be described in detail with reference to the accompanying drawings according to certain embodiments. 
         [0018]    First, a lithium polymer battery will be described according to an embodiment. 
         [0019]      FIG. 1  is a perspective view illustrating the lithium polymer battery  100  according to an embodiment.  FIG. 2  is a sectional view of the lithium polymer battery  100  taken along line I-I′ of  FIG. 1 .  FIG. 3  is an enlarged sectional view illustrating portion (3) of  FIG. 2 .  FIG. 4  is a perspective view illustrating a sealed outer member  120  of the lithium polymer battery  100  illustrated in  FIG. 1 .  FIG. 5  is a perspective view illustrating a folded state of the sealed outer member  120  of the lithium polymer battery  100  illustrated in  FIG. 4 . 
         [0020]    As shown in  FIGS. 1 through 5 , the lithium polymer battery  100  of the current embodiment may include an electrode assembly  110 , the outer member  120 , a protective circuit module  130 , and insulation tapes  140 . 
         [0021]    The outer member  120  of the lithium polymer battery  100  may be sealed, and upper and lower remaining parts  124  and  126  of the outer member  120  may be folded. The insulation tapes  140  may be attached to edge parts (B) of the folded outer member  120 . For attaching the insulation tapes  140  to the edge parts (B), the edge parts (B) are pressed to defined recesses having a depth corresponding to the thickness of the insulation tapes  140 . Since the insulation tapes  140  are attached to the pressed edge parts (B), a thickness (T) of the lithium polymer battery  100  is not increased. 
         [0022]    The electrode assembly  110  may include a positive electrode plate  111 , a separator  113 , and a negative electrode plate  112  that are sequentially stacked or wound after being sequentially stacked. A positive electrode tab  114  may be connected to the positive electrode plate  111  and extend outward from the positive electrode plate  111  by a predetermined length, and a negative electrode tab  115  may be connected to the negative electrode plate  112  and extend outward from the negative electrode plate  112  by a predetermined length. 
         [0023]    The positive electrode plate  111  may be formed by coating aluminum foil or mesh with a lithium cobalt oxide (positive electrode active material). The negative electrode plate  112  may be formed by coating copper foil with graphite (negative electrode active material). The separator  113  may be formed of a gel type polymer electrolyte. However, the separator  113  is not limited to the gel type polymer electrolyte. In addition, the current embodiment is not limited to the positive electrode plate  111 , the positive electrode active material, the negative electrode plate  112 , and the negative electrode active material. 
         [0024]    The positive electrode tab  114  may be formed of aluminum and may be connected to a non-coating portion of the positive electrode plate  111 . The positive electrode tab  114  may protrude from a side of the outer member  120 . The negative electrode tab  115  may be formed of copper and may be connected to a non-coating portion of the negative electrode plate  112 . The negative electrode tab  115  may protrude from a side of the outer member  120 . However, the current embodiment is not limited to the above-listed materials. 
         [0025]    The outer member  120  may include a plurality of layers. The outer member  120  may include a metal thin film  120   a  and insulation layers  120   b  and  120   c  formed on both sides of the metal thin film  120   a.    
         [0026]    The metal thin film  120   a  may be formed of steel, stainless steel, aluminum, or an equivalent thereof. However, the material of the metal thin film  120   a  is not limited to the above-mentioned materials. 
         [0027]    The insulation layers  120   b  and  120   c  may include an outer insulation layer  120   b  and an inner insulation layer  120   c.    
         [0028]    The outer insulation layer  120   b  may foam an outer surface of the outer member  120 . The outer insulation layer  120   b  may be formed of one of nylon, polyethylene terephthalate (PET), and an equivalent thereof. However, the material of the outer insulation layer  120   b  is not limited to the above-mentioned materials. 
         [0029]    The inner insulation layer  120   c  forms an inner surface of the outer member  120 . The inner insulation layer  120   c  may be formed of one of chlorinated polypropylene (CPP) and an equivalent thereof. However, the material of the inner insulation layer  120   c  is not limited to the above-mentioned materials. 
         [0030]    The outer member  120  may include an upper outer member  121  and a lower outer member  122 . Edges of the upper outer member  121  and the lower outer member  122  may be bonded together, and the other edges of the upper outer member  121  and the lower outer member  122  may not be bonded so that the electrode assembly  110  can be received. 
         [0031]    The upper outer member  121  may include a drawing part  123  and the upper remaining part  124  extending from the drawing part  123 . The drawing part  123  can accommodate the electrode assembly  110 . 
         [0032]    The lower outer member  122  may include a finishing part  125  and the lower remaining part  126 . The finishing part  125  may cover the drawing part  123 . The lower remaining part  126  corresponds to the upper remaining part  124  of the upper outer member  121 . The upper remaining part  124  and the lower remaining part  126  are brought into contact with each other to seal the lithium polymer battery  100 . 
         [0033]    The drawing part  123  may be formed into a shape corresponding to the shape of the electrode assembly  110 . The drawing part  123  can include a top surface  123   a  having a predetermined area, and side surfaces  123   b ,  123   c ,  123   d , and  123   e  extending from the top surface  123   a . The depth of the drawing part  123  may be determined by the side surfaces  123   b ,  123   c ,  123   d , and  123   e . In the following description, a side of the lithium polymer battery  100  from which the positive and negative electrode tabs  114  and  115  protrude will be referred to as a “front surface”  123   b . Sides of the upper and lower outer members  121  and  122  that are bonded together will be referred to as a “rear surface”  123   e . Remaining parts are not formed at the rear surface  123   e . The other side surfaces except for the front surface  123   b  and the rear surface  123   e  will be referred to as a “first side surface”  123   c  and a “second side surface”  123   d.    
         [0034]    The upper remaining part  124  may include a first remaining part  124   a  extending from the front surface  123   b , a second remaining part  124   b  extending from the first side surface  123   c , and a third remaining part  124   c  extending from the second side surface  123   d.    
         [0035]    Corners  127  may be formed on both sides of the front surface  123   b  of the upper remaining part  124 . The corners  127  facing the protective circuit module  130  may be diagonally cut. The second remaining part  124   b  and the third remaining part  124   c  may be folded and brought into contact with the first side surface  123   c  and the second side surface  123   d , respectively. The heights of the folded second and third remaining parts  124   b  and  124   c  may be equal to or less than the heights of the first and second side surfaces  123   c  and  123   d.    
         [0036]    The top surface  123   a  may include stepped parts  128 . The top surface  123   a  has an area corresponding to the size of the electrode assembly  110  accommodated in the drawing part  123 . 
         [0037]    The stepped parts  128  may be disposed at both sides of the top surface  123   a . The insulation tapes  140  may be attached to the stepped parts  128 , respectively. The stepped parts  128  may be formed by a pressing process. A depth (A) formed by the pressing process may be substantially equal to the thickness of the insulation tapes  140 . Therefore, the insulation tapes  140  may be at a level not substantially higher than the top surface  123   a  after the insulation tapes  140  are attached to the stepped parts  128 . 
         [0038]    The protective circuit module  130  may include a protective circuit board. A plurality of semiconductor devices may be disposed on the protective circuit board to detect overcharging, overdischarging, and short circuit of the lithium polymer battery  100 . The protective circuit module  130  may include electrode terminal  131  for charge and discharge. 
         [0039]    The protective circuit module  130  may be electrically connected to the positive electrode tab  114  and the negative electrode tab  115 . The protective circuit module  130  may be easily erected at the front side of the outer member  120  (pouch) by bending the positive and negative electrode tabs  114  and  115  in an L or U shape. 
         [0040]    When the protective circuit module  130  is erected, the height of the protective circuit module  130  may be substantially equal to or less than the lateral height of the drawing part  123 . 
         [0041]    Each of the insulation tapes  140  may include an insulation part  141  and an adhesive part  142 . 
         [0042]    The insulation part  141  may be formed of a heat-resistant and chemical-resistant material. For example, the insulation part  141  may be formed of a material selected from the group consisting of a polyethylene film, an epoxy film, a polyimide film, a Teflon film, a polyvinyl chloride film, a polyester film, an acetate film, a filament film, an asbestos film, a paper film, and a polypropylene film. 
         [0043]    The adhesive part  142  may be formed on a side of the insulation part  141 . The adhesive part  142  may include one of an acryl-based adhesive, a silicon-based adhesive, and a rubber-based adhesive. 
         [0044]    The insulation tapes  140  may be attached in a reverse L shape. The thickness of the insulation tapes  140  may be about 50 μm or less. The length of the insulation tapes  140  may correspond to the length of the edge parts (B) of the second remaining part  124   b  and the third remaining part  124   c.    
         [0045]      FIG. 6  is a flowchart explaining a method of manufacturing a lithium polymer battery  100  according to an embodiment. 
         [0046]    The lithium polymer battery manufacturing method of the current embodiment includes: an operation S 10  of preparing an outer member  120 ; an operation S 20  of accommodating and sealing an electrode assembly  110  including positive and negative electrode tabs  114  and  115  in the outer member  120 ; an operation S 30  of pressing both sides of a top surface  123   a  of a drawing part  123  of the sealed outer member  120  to form recesses heaving a depth corresponding to the thickness of insulation tapes  140 ; an operation S 40  of connecting a protective circuit module  130  to the positive and negative electrode tabs  114  and  115 ; and an operation S 50  of attaching the insulation tapes  140  to both the pressed sides of the top surface  123   a  of the drawing part  123  of the outer member  120 . 
         [0047]    In the lithium polymer battery manufacturing method of the current embodiment, after performing the operation S 20  of accommodating and sealing the electrode assembly  110  in the outer member  120 , the operation S 40  of connecting the protective circuit module  130  to the positive and negative electrode tabs  114  and  115 , the operation S 30  of pressing both sides of the top surface  123   a  of the drawing part  123  to form recesses heaving a depth corresponding to the thickness of the insulation tapes  140 , and the operation S 50  of attaching the insulation tapes  140  to both the pressed sides of the top surface  123   a  may be sequentially performed. 
         [0048]    In the outer member preparing operation S 10 , the outer member  120  is prepared, and the outer member  120  may include an upper outer member  121  and a lower outer member  122  that can be folded. The upper outer member  121  may include the drawing part  123  and an upper remaining part  124  extending from the drawing part  123 . The drawing part  123  may accommodate the electrode assembly  110 . The lower outer member  122  may include a finishing part  125  and a lower remaining part  126 . The finishing part  125  can cover the drawing part  123 . 
         [0049]    In the sealing operation S 20 , the electrode assembly  110  may be accommodated in the drawing part  123 , and the upper remaining part  124  of the upper outer member  121  and the lower remaining part  126  of the lower outer member  122  may be brought into contact with each other and sealed. A second remaining part  124   b  and a third remaining part  124   c  of the upper remaining part  124  may be folded and brought into contact with a first side surface  123   c  and a second side surface  123   d  of the drawing part  123 , respectively. At this time, metal thin films  120   a  may be exposed along edge parts (B) of the second remaining part  124   b  and the third remaining part  124   c.    
         [0050]    In the pressing operation S 30 , both sides of the top surface  123   a  may be pressed to a depth corresponding to the thickness of the insulation tapes  140 . By this, stepped parts  128  can be formed. The insulation tapes  140  may be attached to the stepped parts  128 , respectively. A width (W) of an area to which the insulation tape  140  is attached may include the width of the stepped part  128  and the thickness of the folded second remaining part  124   b . For example, the width (W) may be about 4 mm to about 5 mm from a lateral edge of the top surface  123   a  of the drawing part  123 . 
         [0051]    In the protective circuit module connecting operation S 40 , the protective circuit module  130  may be connected to the positive electrode tab  114  and the negative electrode tab  115 . The protective circuit module connecting operation S 40  may include an operation of bending the positive electrode tab  114  and the negative electrode tab  115  in an L or U shape: 
         [0052]    In the insulation tape attaching operation S 50 , the insulation tapes  140  may be attached to both sides of the top surface  123   a . At this time, the insulation tapes  140  may be attached in a manner such that the metal thin films  120   a  exposed along the edge parts (B) of the second remaining part  124   b  and the third remaining part  124   c  are covered with the insulation tapes  140 . Each of the insulation tapes  140  may include an adhesive part  142 . In the operation S 50 , first, the insulation tape  140  may be placed toward the stepped part  128 . Then, the adhesive part  142  may be attached to the stepped part  128 . The insulation tapes  140  may be attached in a manner such that the folded second and third remaining parts  124   b  and  124   c  are entirely covered with the insulation tapes  140 . Although the folded second and third remaining parts  124   b  and  124   c  are lower than the drawing part  123 , the insulation tapes  140  may be attached to cover the folded second and third remaining parts  124   b  and  124   c . That is, the insulation tapes  140  may be attached to the entire lateral surfaces of the lithium polymer battery  100 . If a thickness (T) of the lithium polymer battery  100  is about 2.7 mm, the insulation tapes  140  may be attached to positions spaced at least 2 mm from the top surface  123   a  of the drawing part  123 . 
         [0053]    A lithium polymer battery will now be described according to another embodiment. 
         [0054]      FIG. 7  is a sectional view illustrating a lithium polymer battery  200  according to another embodiment.  FIG. 7  corresponds to  FIG. 2 .  FIG. 8  is an enlarged sectional view illustrating portion (8) of  FIG. 7 . 
         [0055]    The lithium polymer battery  200  of the current embodiment may include an electrode assembly  110 , an outer member  220 , a protective circuit module  130 , and insulation tapes  240 . Elements such as the electrode assembly  110  and the protective circuit module  130  of the current embodiment may be the same as those of the previous embodiment explained with reference to  FIGS. 1 through 5 . The same elements are denoted by the same reference numerals herein, and therefore not described. 
         [0056]    In the lithium polymer battery  200  of the current embodiment, the insulation tapes  240  have a C-shape as shown in  FIGS. 7 and 8 . The insulation tapes  240  may be attached to both sides of the lithium polymer battery  200  in a manner such that the insulation tapes  240  cover upper and lower regions of both sides of the lithium polymer battery  200 . 
         [0057]    Both sides of a top surface  223   a  of a drawing part  223 , and both sides of a finishing part  225  of a lower outer member  222  may be pressed to form recesses having a depth corresponding to the thickness of the insulation tapes  240 . The top surface  223   a  and the finishing part  225  may be pressed individually or at the same time. First stepped parts  228  may be formed in the top surface  223   a  of the drawing part  223 . Second stepped parts  229  may be formed in the finishing part  225  of the lower outer member  222 . 
         [0058]    A pressed depth (A) of the top surface  223   a  and a pressed depth (C) of the finishing part  225  may be equal to the thickness of the insulation tapes  240 , and thus the thickness of the lithium polymer battery  200  does not increase although the insulation tapes  240  are attached to the top and bottom sides of the lithium polymer battery  200 . 
         [0059]    End parts of the insulation tapes  240  may be placed on the first stepped parts  228  in a manner such that folded second and third remaining parts  224   b  and  224   c  are covered by the insulation tapes  240 , and then the remaining parts of the insulation tapes  240  may be attached to the second stepped parts  229 . 
         [0060]    At this time, since the insulation tapes  240  are attached to the upper and lower regions of both sides of the lithium polymer battery  200  to cover metal thin films  120   a  exposed along edge parts (B) of the second and third remaining parts  224   b  and  224   c , a short circuit may be prevented between the metal thin film  120   a  and an external device. 
         [0061]    Certain embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as set forth in the following claims.