Patent Publication Number: US-2019198851-A1

Title: Rechargeable battery

Description:
TECHNICAL FIELD 
     The present invention relates to a rechargeable battery. 
     BACKGROUND ART 
     Unlike a primary battery that cannot be recharged, a rechargeable battery is a battery that may be charged and discharged. The rechargeable battery is widely used for a small-sized portable electronic device such as a mobile phone, a notebook, or a camcorder or widely used as a power source for operating a motor of a hybrid vehicle. 
     The rechargeable battery has an electrode assembly that includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The electrode assembly is accommodated in a casing and charged and discharged. The casing has a terminal so as to supply or be supplied with electric currents. The casing may be made of metal or polymer. 
     There is an increasing need for the rechargeable battery having a high capacity, and therefore density of a positive electrode active material and density of a negative electrode active material are increased and a thickness of a plate and thicknesses of components are decreased in order to increase the capacity in a state in which an area of the electrode assembly remains the same. Further, a thickness of the separator is also decreased to a thin film level. 
     However, there are problems in that an internal short circuit may occur when impact is applied to the rechargeable battery from the outside, and a temperature is rapidly increased due to contact between a positive electrode plate and a negative electrode active material caused by Joule heating and shrinkage of the separator. 
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in an effort to provide a rechargeable battery capable of preventing an internal short circuit caused by external impact. 
     Technical Solution 
     An exemplary embodiment of the present invention provides a rechargeable battery including: an electrode assembly which is wound and includes a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode; a casing which accommodates the electrode assembly; a first electrode tab which is connected to a non-coated portion of the first electrode; a second electrode tab which is connected to a non-coated portion of the second electrode; and a first insulating tape which is positioned at a winding start portion of the electrode assembly and attached to the non-coated portion of the first electrode so as to at least cover a center of a first curved portion which is curvedly formed as the electrode assembly is wound. 
     The first insulating tape may be attached to a coated portion of the first electrode which is coated with an active material. 
     The first insulating tape may be attached to cover 1 mm to 2 mm of a coated portion of the first electrode which is coated with an active material. 
     The non-coated portion of the first electrode may further include a second insulating tape which is attached, along the first insulating tape, to a surface opposite to the surface to which the first insulating tape is attached. 
     A melting point of the first insulating tape may be higher than a melting point of the separator. 
     The first insulating tape may be made of any one of polyamide (PA), polyimide (PI), and ceramic. 
     A melting point of the first insulating tape may be 200° C. or higher. A winding end portion of the electrode assembly may further include a fixing tape which is attached to the non-coated portion of the first electrode. 
     Advantageous Effects 
     According to the exemplary embodiment of the present invention, it is possible to improve safety of the rechargeable battery by preventing an internal short circuit caused by an external impact. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a rechargeable battery according to an exemplary embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of the rechargeable battery illustrated in  FIG. 1 . 
         FIG. 3  is a cross-sectional view schematically illustrating a cross section of an electrode assembly according to a first exemplary embodiment. 
         FIG. 4  is a view illustrating a state in which an electrode assembly according to a second exemplary embodiment is disassembled. 
         FIG. 5  is a view illustrating the first exemplary embodiment in which the electrode assembly illustrated in  FIG. 4  is wound once. 
         FIG. 6  is a view illustrating the second exemplary embodiment in which the electrode assembly illustrated in  FIG. 4  is wound once. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the scope of the present invention. 
     A part irrelevant to the description will be omitted to clearly describe the present invention, and the same or similar constituent elements will be designated by the same reference numerals throughout the specification. 
     In addition, a size and a thickness of each constituent element illustrated in the drawings are arbitrarily shown for understanding and ease of description, but the present invention is not limited thereto. 
     In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
       FIG. 1  is a perspective view illustrating a rechargeable battery according to an exemplary embodiment of the present invention, and  FIG. 2  is an exploded perspective view of the rechargeable battery illustrated in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a rechargeable battery  100  is disclosed. For example, the rechargeable battery according to the exemplary embodiment of the present invention may be a pouch type rechargeable battery. The pouch type rechargeable battery  100  includes an electrode assembly  10 , and a pouch casing  30  that accommodates the electrode assembly  10 . 
     The pouch casing  30  may include an accommodating portion  31 , a rim joint portion  33 , and an upper joint portion  32 . 
     The pouch casing  30  may be sealed as a first plate  30   a  and a second plate  30   b  are coupled to each other. The first plate  30   a  and the second plate  30   b  of the pouch casing  30  are formed to have a multilayered sheet structure. For example, the pouch casing  30  may include a metal sheet or a polymer sheet. The polymer sheet defines an inner surface of the pouch to perform insulating and thermal bonding functions, and defines an outer surface of the pouch to perform a protecting function. As an example, the polymer sheet may be a nylon sheet, a polyethylene terephthalate (PET) sheet, or a PET-nylon composite sheet. The metal sheet provides mechanical strength and may be an aluminum sheet, for example. 
     The accommodating portion  31  accommodates the electrode assembly  10  and may be formed in any one of the first plate  30   a  and the second plate  30   b  of the pouch casing  30 . The upper joint portion  32  may be formed at an upper end of the accommodating portion  31 , and a first lead tab  21  and a second lead tab  22 , which are electrically connected to the electrode assembly  10 , may be extended from the upper joint portion  32 . The first lead tab  21  is electrically connected to a first electrode tab  11   a  of the electrode assembly  10 , and the second lead tab  22  is electrically connected to a second electrode tab  12   a  of the electrode assembly  10 . 
     At the upper joint portion  32 , the first plate  30   a  and the second plate  30   b  of the pouch casing  30  may be joined together by thermal bonding. The rim joint portion  33  is formed at a lateral side of the accommodating portion  31 , and the first plate  30   a  and the second plate  30   b  may be joined together by thermal bonding at the rim joint portion  33 . 
     At the upper joint portion  32 , protective tapes  23  and  24  may be attached to the first lead tab  21  and the second lead tab  22 , respectively. Therefore, it is possible to prevent a risk that the pouch casing  30  comes into contact with the first and second lead tabs  21  and  22 , which causes a short circuit. The first and second lead tabs  21  and  22 , to which the protective tapes  23  and  24  are attached, respectively, are positioned between the first plate  30   a  and the second plate  30   b  at the upper joint portion  32 , and as a result, the upper joint portion  32  may be greater in thickness than the rim joint portion  33 . 
       FIG. 3  is a cross-sectional view schematically illustrating a cross section of an electrode assembly according to a first exemplary embodiment. 
     Referring to  FIG. 3 , the electrode assembly  10 , which is charged with an electric current and discharged, may include a first electrode  11 , a second electrode  12 , and a separator  13  interposed between the first electrode  11  and the second electrode  12 . 
     The first electrode  11  and the second electrode  12  may include, respectively, electrode plates, coated portions  11   b  and  12   b  which are formed by coating at least one surface of each of the electrode plates with an active material, non-coated portions  11   c  and  12   c  which are not coated with an active material and extend from one side of the coated portions  11   b  and  12   b , and the first electrode tab  11   a  and the second electrode tab  12   a  which are connected to the non-coated portions  11   c  and  12   c , respectively. 
     The first electrode tab  11   a  and the second electrode tab  12   a  may be electrically connected to the first lead tab  21  (see  FIG. 2 ) and the second lead tab  22  (see  FIG. 2 ), respectively. For example, the first electrode  11  may be a positive electrode, and the positive electrode may include the positive electrode plate which is formed as a metal thin plate having a strip shape, and the coated portion  11   b  which is formed by coating one surface or both surfaces of the positive electrode plate with a positive electrode active material. The positive electrode plate may be configured as a thin plate made of metal, for example, aluminum having excellent conductivity. The positive electrode active material applied onto the coated portion  11   b  may be a material made by mixing a binder, a conductive material, and the like with lithium-based oxide. The second electrode  12  may be a negative electrode, and the negative electrode may include a negative electrode plate which is formed as a metal thin plate having a strip shape, and the coated portion  12   b  which is formed by coating one surface or both surfaces of the negative electrode plate with a negative electrode active material. The negative electrode plate may be configured as a thin plate made of metal, for example, copper having excellent conductivity. The negative electrode active material applied onto the coated portion  12   b  may be a material made by mixing a binder, a conductive material, and the like with a negative electrode active material such as carbon. 
     The separator  13  may be made of a porous material. For example, the separator  13  may be made of any one of polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP). The separator  13  may be shrunk and deformed at a temperature of 150° C. or less. 
     The electrode assembly  10  may be formed in the form of a jelly roll by interposing the separator  13  between the first electrode  11  and the second electrode  12 , winding the electrode assembly  10  about a winding axis several times, and then pressing the electrode assembly  10  flat. The first electrode tab  11   a  and the second electrode tab  12   a  may be positioned adjacent to a winding center so as to minimize a magnetic field that occurs due to a flow of the electric current during the discharging. 
     The first electrode  11  includes the non-coated portion  11   c  that may be wound around an outer periphery of the wound electrode assembly  10  while making one or more revolutions. In addition, at the winding center, the first electrode tab  11   a  is connected to the non-coated portion  11   c.    
     The second electrode  12  includes the non-coated portion  12   c  to which the second electrode tab  12   a  is connected at the winding center. In this case, at the winding center, the non-coated portion  12   c  of the second electrode  12  is longer than the non-coated portion  11   c  of the first electrode  11 . 
     A first insulating tape  41  and a second insulating tape  42  are attached to the first electrode tab  11   a  so as to prevent the first electrode tab  11   a  from being brought into contact with the non-coated portion  12   c  of the second electrode  12  and the coated portion  12   b  of the second electrode  12 . Each of the first insulating tape  41  and the second insulating tape  42  is configured as a high heat-resistant insulating tape having high heat resistance. 
     The high heat-resistant insulating tape may be an insulating tape that has a higher melting point than the separator  13 . As an example, the melting point of the high heat-resistant insulating tape may be 200° C. or higher. The high heat-resistant insulating tape may be made of any one of organic materials such as polyimide (PI) and polyamide (PA) and inorganic materials such as ceramic. 
     In general, the separator  13  may begin to be shrunk and deformed at a temperature of 150° C. or less. Since the electrode assembly  10  is wound and then pressed flat as described above, the electrode assembly  10  has a curved portion  15  (see  FIG. 2 ) curvedly formed at a lateral side of the electrode assembly  10 . The curved portions  15  are formed at left and right sides of the electrode assembly  10 . 
     The first insulating tape  41  may be attached so as to at least cover a center of a first curved portion  15   a . A length L 1  of the attached first insulating tape  41  is longer than a curve length C to the center of the first curved portion  15   a . That is, the first insulating tape  41  is attached so as to cover the center of the curved portion which is a weak portion of the first curved portion  15   a , and the length L 1  of the attached first insulating tape  41  is longer than the curve length C which is a distance to the center of the curved portion. Therefore, it is possible to prevent the second electrode  12  from being short-circuited at the center of the first curved portion  15   a.    
     The second insulating tape  42  may be attached to a surface of the electrode plate of the first electrode  11  which is opposite to the surface to which the first insulating tape  41  is attached. A length L 2  of the attached second insulating tape  42  may be equal to the length of the attached first insulating tape  41 . 
     A winding end portion of the electrode assembly  10  may further include a fixing tape  50 , which is attached to the non-coated portion  11   c  of the first electrode  11 . 
       FIG. 4  is a view illustrating a state in which an electrode assembly according to a second exemplary embodiment is disassembled,  FIG. 5  is a view illustrating the first exemplary embodiment in which the electrode assembly illustrated in  FIG. 4  is wound once, and  FIG. 6  is a view illustrating the second exemplary embodiment in which the electrode assembly illustrated in  FIG. 4  is wound once. 
     Referring to  FIGS. 4 and 6 , the separator  13 , the second electrode  12 , the separator  13 , and the first electrode  11  may be stacked in this order and then wound counterclockwise so as to manufacture the electrode assembly  10 . 
     At a winding start portion, the non-coated portion  12   c  of the second electrode  12  is longer than the non-coated portion  11   c  of the first electrode  11 , and the second electrode tab  12   a  is connected to the non-coated portion  12   c  of the second electrode  12 . The second electrode  12  includes the coated portion  12   b  which is formed by coating at least one surface of the electrode plate of the second electrode  12  with an active material. The coated portion  12   b  is formed on one surface of the electrode plate of the second electrode  12  and on a straight portion from the first curved portion  15   a  to a second curved portion  15   b.    
     At the winding start portion, the non-coated portion  11   c  of the first electrode  11  is shorter than the non-coated portion  12   c  of the second electrode  12 , and the first electrode tab  11   a  is connected to the non-coated portion  11   c  of the first electrode  11 . Because of the difference in length, the first electrode tab  11   a  and the second electrode tab  12   a  may be positioned at the left and right sides based on the winding center, respectively. The first electrode tab  11   a  and the second electrode tab  12   a  may be positioned adjacent to each other in order to minimize a magnetic field occurring when discharging an electric current. 
     The first electrode  11  includes the coated portion  11   b  which is formed by coating at least one surface of the electrode plate with an active material. The coated portions  11   b  are formed on both surfaces of the electrode plate of the first electrode  11  and on a straight portion from the first curved portion  15   a  to the second curved portion  15   b.    
     The first insulating tape  41  and the second insulating tape  42  are attached to the first electrode  11 , and the first insulating tape  41  may be attached to the first electrode tab  11   a  and an upper surface of the non-coated portion  11   c  of the first electrode  11 . The second insulating tape  42  may be attached to a lower surface of the non-coated portion  11   c  of the first electrode  11 . 
     For example, the first insulating tape  41  may be attached to the coated portion  11   b  of the first electrode  11  which is coated with the active material. In addition, the second insulating tape  42  may be attached to the coated portion  11   b  of the first electrode  11  which is coated with the active material. As another example, the first insulating tape  41  may be attached to cover about 1 mm to about 2 mm of the coated portion  11   b  of the first electrode  11  which is coated with the active material. In addition, the second insulating tape  42  may be attached to cover about 1 mm to about 2 mm of the coated portion  12   b  of the first electrode  12  which is coated with the active material. 
     There is a great risk that the center of the curved portion  15 , which is formed curvedly as the electrode assembly is wound, will be short-circuited due to contact between the first electrode  11  and the second electrode  12  even by a small external impact. Therefore, the insulating tape may be attached to the coated portion  11   b  while covering the first curved portion  15   a.    
     In addition, the first insulating tape  41  is attached to the first electrode tab  11   a . The reason is that there is a great risk that similar to the center of the curved portion  15 , the first electrode tab  11   a  will be short-circuited by being brought into contact with the second electrode  12  even by a small external impact because the first electrode tab  11   a  is connected to the non-coated portion  11   c  of the first electrode  11  and protrudes from the non-coated portion  11   c  of the first electrode  11 . The first insulating tape  41  prevents the non-coated portion  11   c  of the first electrode  11  from being exposed in a direction toward the second electrode  12  at the winding start portion, thereby preventing a short circuit that may occur due to an external impact. 
     While the present invention has been described with reference to the aforementioned exemplary embodiments, the person skilled in the art will easily understand that the present invention is not limited to the disclosed exemplary embodiments, but can be variously corrected and modified without departing from the scope of the appended claims. 
     
       
         
           
               
             
               
                   
               
               
                 &lt;Description of symbols&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 100: Rechargeable battery 
                 10: Electrode assembly 
               
               
                 11: First electrode 
                 12: Second electrode 
               
               
                 11a: First electrode tab 
                 11b, 12b: Coated portion 
               
               
                 12a: Second electrode tab 
                 11c, 12c: Non-coated portion 
               
               
                 13: Separator 
                 15: Curved portion 
               
               
                 15a: First curved portion 
                 15b: Second curved portion 
               
               
                 21: First lead tab 
               
               
                 22: Second lead tab 
                 23, 24: Protective tape 
               
               
                 30: Pouch casing 
                 30a: First plate 
               
               
                 30b: Second plate 
                 31: Accommodating portion 
               
               
                 32: Upper joint portion 
                 33: Rim joint portion 
               
               
                 41: First insulating tape 
                 42: Second insulating tape 
               
               
                 50: Fixing tape 
               
               
                 L1: Length of attached first insulating tape 
                 C: Curve length 
               
               
                 L2: Length of attached second insulating 
               
               
                 tape