Patent Publication Number: US-2015086858-A1

Title: Rechargeable battery

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/881,826, filed on Sep. 24, 2013, in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. Any and all priority claims identified in the Application Data Sheet, or any correction thereto, are hereby incorporated by reference under 37 CFR 1.57. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a rechargeable battery having an insulating case interposed between an electrode assembly inserted into an outer case and a cap plate. 
     2. Description of the Related Technology 
     A rechargeable battery performs repetitive charging and discharging, unlike the primary battery. A small-capacity rechargeable battery is used in small-sized portable electronic devices, such as a mobile phone, a laptop, and a camcorder, and a large-capacity battery is used as a power source for motor drive, such as an electric bicycle, a scooter, an electric vehicle, a fork lift, and the like. 
     The rechargeable battery includes an electrode assembly in which a positive electrode and a negative electrode are laminated with a separator therebetween and then wound in a jelly roll type, an outer case containing the electrode assembly together with an electrolyte therein, a cap plate sealing an opening formed in an upper end of the outer case, an electrode terminal installed on the cap plate and electrically connected to the electrode assembly, and an insulating case installed between the electrode assembly and the cap plate. 
     During assembly of the rechargeable battery, in the processes of inserting the electrode assembly into the outer case, inserting the insulating case into the outer case, and inserting the cap plate into the opening of the outer case, metal foreign substances (e.g., residual foreign substances of parts and external substances) may flow into the opening of the outer case. 
     After the electrode assembly is inserted into the outer case, the metal foreign substances flowing into the opening of the outer case may cause an electric circuit between the outer case and the electrode assembly in the opening of the outer case. Therefore, safety of the rechargeable battery may be deteriorated. 
     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 OF CERTAIN INVENTIVE ASPECTS 
     The described technology has been made in an effort to provide a rechargeable battery having an advantage of improving safety thereof by preventing an outer case and an electrode assembly from short-circuiting due to metal foreign substances in an opening of the outer case, after the electrode assembly is inserted into the outer case. 
     One embodiment provides a rechargeable battery including: an electrode assembly; an outer case configured to enclose the electrode assembly, wherein the outer case includes an opening; a cap plate configured to seal the opening of the outer case; an insulating case of a predetermined height installed within the outer case, the insulating case installed between the cap plate and the electrode assembly; and an electrode terminal installed on the cap plate and electrically connected to the electrode assembly, wherein the outer case includes an insulating portion formed on an inner surface of the opening thereof adjacent said insulating case, said insulating portion being electrically insulating, and said insulating portion located at an upper portion of the outer case and being shaped to prevent foreign substances from flowing from the external environment into the outer case. 
     The rechargeable battery may further include an electrolyte, wherein the outer case is configured to enclose the electrolyte; and the insulating portion is insoluble in the electrolyte. 
     The insulating case may be formed with a step difference from the opening of the outer case. 
     The insulating portion may have a first height between the opening and the electrode assembly, where the first height may be larger than the predetermined height of the insulating case. 
     A lower surface of the insulating portion may be closer to the electrode assembly than a lower surface of the insulating case. 
     The insulating portion may include at least one of polyimide, epoxy, or polypropylene. 
     The insulating portion may have a uniform thickness along its height. 
     The insulating portion may have an inclined structure along it height, wherein the insulating portion is gradually thickened in a direction from the opening of the electrode assembly. 
     The insulating portion may have a concave-convex structure along its height. 
     The outer case may include two flat surface portions and two curved portions surrounding the flat surface portions, and wherein the insulating portion has a maximum thickness in a direction between the outer case and the insulating case. 
     The insulating portion may include a plurality of grooves and protrusions alternately arranged between the insulating case and the outer case. 
     The insulating portion may surround the insulating case. 
     The thickness of the insulating portion may be from about 8 to about 20 micrometers. 
     According to one embodiment, a method of producing a rechargeable battery, includes: providing an electrode assembly; forming an insulating portion on an upper portion of an inner surface of an outer case, wherein the outer case includes an opening above the upper portion; enclosing the electrode assembly in the outer case; installing an insulating case of a predetermined height within the outer case, whereby the insulating case is adjacent the insulating portion; sealing the opening of the case with the cap plate, whereby the insulating case is between the cap plate and the electrode assembly; installing an electrode terminal on the cap plate, said electrode terminal being electrically connected to the electrode assembly. 
     Forming the insulating portion may include spray coating using an ink jet nozzle. 
     Forming the insulating portion may include electro-deposition coating. 
     The method of producing the rechargeable battery may further include injecting an electrolyte through an electrolyte injection port in the cap plate. 
     The thickness of the insulating portion formed may be from about 8 to about 20 micrometers. 
     According to some embodiments, the insulating portion is formed on an inner surface of the case, corresponding to a space between the cap plate and the electrode assembly, so that the case and the electrode assembly can be prevented from short circuiting therebetween due to metal foreign substances in the opening of the case, after the insertion of the electrode assembly into the case. Safety of the rechargeable battery can thus be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a rechargeable battery according to one embodiment; 
         FIG. 2  is a cross-sectional view taken along line II-II in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a case taken along line II-II in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of a case taken along line IV-IV in  FIG. 1 ; 
         FIG. 5  is a partial cross-sectional view of a case used in a rechargeable battery according to one embodiment; 
         FIG. 6  is a partial cross-sectional view of a case used in a rechargeable battery according to one embodiment; 
         FIG. 7  is a plane view of a case used in a rechargeable battery according to one embodiment; 
         FIG. 8  is a partial cross-sectional view of a case used in a rechargeable battery according to one embodiment; and 
         FIG. 9  is a plane view of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS 
     Hereinafter, the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various ways, without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals generally designate like elements throughout the specification. 
       FIG. 1  is an exploded perspective view of a rechargeable battery according to one embodiment, and  FIG. 2  is a cross-sectional view taken along line II-II in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a rechargeable battery includes: an electrode assembly  10  performing charging and discharging; an outer case  20  containing the electrode assembly  10  together with an electrolyte; a cap plate  30  sealing an opening formed in an upper end of the outer case  20 ; an insulating case  60  installed between the cap plate  30  and the electrode assembly  10 ; and an electrode terminal  40  installed in a terminal hole  31  of the cap plate  30  and electrically connected to the electrode assembly  10 . In addition, the rechargeable battery further includes a terminal plate  50  for electrically connecting the electrode terminal  40  to the electrode assembly  10 . 
     The electrode assembly  10  has a shape corresponding to an inner space of the outer case  20  having a rectangular shape, such that the electrode assembly  10  is inserted into the outer case  20 . For example, the outer case  20  includes a flat surface portion  201  corresponding to a plane of the electrode assembly  10  and a curved surface portion  202  formed at both sides of the flat surface portion  201  to correspond to a curved surface of the electrode assembly  10 . 
     The case contains the electrode assembly  10  therein through the opening, and is formed of a conductor to function as an electrode terminal. For example, the outer case  20  may be formed of aluminum or an aluminum alloy. 
     The electrode assembly  10  is formed by laminating a positive electrode  11  and a negative electrode  12  on both surfaces of a separator  13  formed of an insulator, the separator  13  being interposed between the positive electrode  11  and the negative electrode  12 , and then winding them in a jelly roll type. The electrode assembly  10  has a positive electrode lead tap  14  connected to the positive electrode  11  and a negative electrode lead tap  15  connected to the negative electrode  12 . 
     The positive electrode lead tap  14  is connected to a lower surface of the cap plate by welding, and the outer case  20  is electrically connected to the positive electrode  11  of the electrode assembly  10  through the cap plate  30  to thereby function as a positive electrode terminal. 
     The negative electrode lead tap  15  is connected to a lower surface of a terminal plate  50  connected to one end of the electrode terminal  40  by welding, and the electrode terminal  40  provided in the terminal hole  31  of the cap plate  30  is electrically connected to the negative electrode  12  of the electrode assembly  10  to thereby function as a negative electrode terminal. 
     Although not shown, the negative electrode lead tap may be connected to the cap plate to allow the case to function as a negative electrode terminal, and the positive electrode lead tap may be connected to the electrode terminal to allow the electrode terminal to function as a positive electrode terminal. 
     The electrode terminal  40  is inserted into the terminal hole  31  of the cap plate  30  by interposing an insulating gasket  41  therebetween. That is, the insulating gasket  41  electrically insulates the terminal hole  31  and the electrode terminal from each other, and forms a sealing structure between the terminal hole  31  and the electrode terminal  40 . 
     The terminal plate  50  is electrically connected to the electrode terminal  40  with an insulating plate  55  interposed therebetween. That is, the insulating plate  55  electrically insulates the cap plate  30  and the terminal plate  50  from each other, and further forms a sealing structure between the cap plate  30  and the terminal plate  50 . 
     The cap plate  30  further has an electrolyte injection port  32 . The electrolyte injection port  32  enables the electrolyte to be injected into the outer case  20  after the cap plate  30  is coupled with the outer case  20 . After injecting the electrolyte, the electrolyte injection port  32  is sealed by a sealing stopper  33 . 
     The insulating case  60  is installed between the electrode assembly  10  and the terminal plate  50  to electrically insulate the electrode assembly  10  and the terminal plate  50  from each other. That is, the insulating case  60  electrically insulates the positive electrode  11  of the electrode assembly  10  and the terminal plate  50  having negative polarity. 
     In addition, the insulating case  60  has tap holes  141  and  151  penetrating the positive electrode lead tap  14  and the negative electrode lead tap  15 , respectively. Therefore, the positive electrode tap  14  may be connected to the cap plate  30  with passing through the tap hole  141 , and the negative electrode lead tap  15  may be connected to the terminal plate  50  with passing through the tap hole  151 . 
       FIG. 3  is a cross-sectional view of a case taken along line II-II in  FIG. 1 , and  FIG. 4  is a cross-sectional view of a case taken along line IV-IV in  FIG. 1 . 
     Referring to  FIGS. 3 and 4 , an insulating portion  70  formed of an electrical insulator is provided on an inner surface of the outer case  20 , which corresponds to a space between the cap plate  30  and the electrode assembly  10 . For example, the insulating portion  70  is formed of polyimide, epoxy, or polypropylene, and thus has an electrical insulating property and a property of being insoluble in an electrolyte. 
     In addition, as shown in  FIG. 4 , the insulating portion  70  may be coated on a portion of the opening of the outer case  20  by a spray method while an ink jet nozzle N is inserted into the outer case  20 . Although not shown, the insulating portion  70  may be coated on the portion of the opening of the case by electro-deposition coating (not shown). 
     The outer case  20  has a step difference portion  21  in the opening to thereby support the cap plate  30 . The step difference portion  21  temporarily fix the cap plate  30  to prevent the cap plate  30  from being excessively inserted into the outer case  20  and facilitate welding of the cap plate  30  in the opening of the outer case  20 . 
     The insulating portion  70  has a first width (W1), which is set from the step difference portion  21  toward the electrode assembly  10  (i.e., height direction (z-axis direction)). The first width (W1) is set to be larger than a second width (W2) of the case  60 . 
     That is, while the insulating case  60  is contacted with an inner surface of the cap plate  30 , a lower end of the insulating portion  70  is lower than a lower end of the insulating case  60 . Here, the electrode assembly  10  is located on a lower surface of the insulating case  60 , and the an upper end of the electrode assembly  10  is located correspondingly to the insulating portion  70 . 
     In addition, the insulating portion  70  may have a uniform thickness in a direction of the first width (W1) (z-axis direction). For example, the insulating portion  70  may have a thickness between about 8 to about 20 μm, such as, for example, 10 μm. Therefore, the insulating portion  70  may have a uniform electrical insulating property against metal foreign substances on the upper end of the electrode assembly  10  and in the opening of the outer case  20 . If the thickness of the insulating portion  70  is smaller than 8 μm, the insulating structure thereof may be easily broken. If the thickness thereof is larger than 20 μm, the electrode assembly  10  may be difficult to insert. 
     Meanwhile, the insulating portion  70  can efficiently prevent the short circuit between the electrode assembly  10  and the outer case  20  even when the rechargeable battery is exposed to heat, and effectively cope with cell swelling due to the internal pressure of the rechargeable battery. 
     Hereinafter, various exemplary embodiments will be set forth. In the following exemplary embodiments, as compared with the first exemplary embodiment and the above-described exemplary embodiment, descriptions of the same elements will be omitted and descriptions of different elements will be made. 
       FIG. 5  is a partial cross-sectional view of a case used in a rechargeable battery according to a second exemplary embodiment. Referring to  FIG. 5 , in the second exemplary embodiment, an insulating portion  270  formed in the opening of the outer case  20  has an inclined structure in which an upper portion is thin and a lower portion is gradually thickened in a direction of the first width (W1) (z-axis). 
     Here, the inclined insulating portion  270  induces the insertion of the electrode assembly  10  through the opening of the outer case  20 , and, after the insertion of the electrode assembly  10 , the inclined insulating portion  270  is closely contacted with the insulating case  60 . Here, a side portion of the upper end of the electrode assembly  10  is located correspondingly to the insulating portion  270 . 
     Therefore, after the insertion of the electrode assembly  10 , the insulating portion  270  can contain foreign substances flowing from the external environment in the inclined upper portion thereof, and can prevent the short circuit between the electrode assembly  10  and the outer case  20 . 
       FIG. 6  is a partial cross-sectional view of a case used in a rechargeable battery according to a third exemplary embodiment. Referring to  FIG. 6 , in the third exemplary embodiment, an insulating portion  370  formed in the opening of the outer case  20  has a concave-convex structure in a direction of the first width (W1) (z-axis direction). 
     The insulating portion  370  having the concave-convex structure does not obstruct the insertion of the electrode assembly  10  through the opening of the outer case  20 , and contains metal foreign substances flowing at the time of the insertion of the electrode assembly  10  in the concave-convex structure. After the insertion of the electrode assembly  10 , the insulating portion  370  having the concave-convex structure is closely contacted with the insulating case  60 . Here, a side portion of the upper end of the electrode assembly  10  is located correspondingly to the insulating portion  370 . 
     Therefore, during and after the insertion of the electrode assembly  10 , the insulating portion  370  can contain foreign substances flowing from the external environment in the concave-convex structure thereof, and prevent the short circuit between the electrode assembly  10  and the outer case  20 . 
       FIG. 7  is a plane view of a case used in a rechargeable battery according to a fourth exemplary embodiment. Referring to  FIG. 7 , in the fourth exemplary embodiment, an insulating portion  470  formed in the opening of the outer case  20  has a maximum thickness (t1) at a curved portion  202 , is gradually thinner toward a flat portion, and has a minimum thickness (t2) at the flat portion, in a direction (x or y axis direction) crossing the direction of the first width (z direction). 
     The insulating portion  470  having a thickness-varying structure does not obstruct the insertion of the electrode assembly through the opening of the outer case  20 , and rakes and contains metal foreign substances flowing at the time of the insertion of the electrode assembly  10 . After the insertion of the electrode assembly  10 , the insulating portion  470  having a large area is closely contacted with the insulating case  60 . Here, a side portion of the upper end of the electrode assembly  10  is closely contacted with the insulating portion  470 . 
     Therefore, during and after the insertion of the electrode assembly  10 , the insulating portion  470  can contain foreign substances flowing from the external environment in the close contact structure having a large area, and prevent the short circuit between the electrode assembly  10  and the outer case  20 . 
       FIG. 8  is a partial cross-sectional view of a case used in a rechargeable battery according to a fifth exemplary embodiment; and  FIG. 9  is a plane view of  FIG. 8 . Referring to  FIGS. 8 and 9 , in the fifth exemplary embodiment, an insulating portion  570  formed in the opening of the outer case  20  is formed in a direction of the first width (z axis direction), and includes grooves  571  and protrusions  572  alternately arranged along a direction (x or y axis direction) crossing the direction of the first width. 
     The insulating portion  570  having grooves  571  and protrusions  572  does not obstruct the insertion of the electrode assembly  10  through the opening of the outer case  20 , and contains metal foreign substances flowing at the time of the insertion of the electrode assembly  10 . After the insertion of the electrode assembly  10 , the insulating portion  570  having grooves  571  and protrusions  572  is closely contacted with the insulating case  60 . Here, a side portion of the upper end of the electrode assembly  10  is closely contacted with the protrusions  572  of the insulating portion  570 . 
     Therefore, during and after the insertion of the electrode assembly  10 , the insulating portion  570  can contain foreign substances flowing from the external environment in the grooves  571  between protrusions  572 , and prevent the short circuit between the electrode assembly  10  and the outer case  20 . 
     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.