Abstract:
A prismatic type lithium secondary battery, including an electrode assembly including an anode plate, a cathode plate, and a separator wound together, a can to receive the electrode assembly via an opening in an upper end thereof, a cap assembly to seal the opening of the can, an insulating case mounted on an upper portion of the electrode assembly once the electrode assembly is inside the can, and a stopping unit, formed in sides of the can to protrude toward the interior of the can, including a support surface to support the cap assembly and a surface to engage with the insulating case.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Korean Application No. 2005-134522, filed Dec. 29, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     Aspects of the present invention relate to a prismatic type lithium secondary battery and, more particularly, to a prismatic type lithium secondary battery and a method of processing a prismatic type lithium secondary battery which simplifies the molding process of the receiving portion of the cap assembly body that seals an upper opening of a can in a prismatic type can.  
         [0004]     2. Description of the Related Art  
         [0005]     A secondary battery is a term for a battery that is capable of being electrically charged and discharged. A primary battery, on the other hand, is not capable of being electrically discharged. A secondary battery may be used in the field of highly technical electronic devices, such as a cellular phone, a note book computer, and a cam coder, etc.  
         [0006]     In particular, a lithium secondary battery has an operating voltage of 3.6 volts, which is approximately 3 times higher than a Nickel-Cadmium battery or a Nickel-Hydrogen battery, each of which may be used as a power source for electronic devices. The lithium secondary battery also has a high characteristic energy density per unit weight.  
         [0007]     The lithium secondary battery in practical use employs a carbon-based material, such as graphite, as a negative electrode, a lithium-containing oxide, such as LiCoO 2 , as a positive electrode, and an organic solvent (e.g., cyclic carbonate, such as ethylene carbonate, a chain carbonate, such as dimethyl carbonate and the like, in which an electrolyte salt, such as LiPF 6  is dissolved, for the electrolyte solution). In such lithium secondary batteries, since a lithium ion moves between the positive electrode and the negative electrode during charging and discharging processes, the energy density of each battery is determined depending on the specific capacity of positive electrode, the specific capacity of negative electrode, the battery specific capacity of positive electrode, the specific capacity of negative electrode, the battery voltage, and the type of the electrolyte solution (i.e., the polymer number of the electrolyte solution).  
         [0008]     In addition, lithium secondary batteries are produced in many various shapes, such as cylinders, prisms, and/or pouches.  
         [0009]      FIG. 1  is a partial sectional view of a conventional prismatic type lithium secondary battery  10 . Here, the prismatic type lithium secondary battery  10  includes a can  11 , an electrode assembly  12 , which is received in the can  11 , and a cap assembly  20 , which seals and which is connected to an upper opening of the can  11 . The can  11  is a prismatic case of a metal material having an inside space. The electrode assembly  12  is a winding in which an anode plate  13 , a separator  14  and cathode plate  15  are wound together. An anode lead  16  and a cathode lead  17  are connected to and serve as outlets for the anode plate  13  and cathode plate  15 , respectively.  
         [0010]     The cap assembly  20  includes a cap plate  21 , which is coupled to the upper portion of the can  11 . A cathode terminal  23  is inserted through the cap plate  21  via a gasket  22 . An insulation plate  24  is mounted on the lower portion of the cap plate  21 . A terminal plate  25 , which communicates with the cathode terminal  23 , is installed on a lower portion of the cap plate  24 . An electrolyte liquid injecting hole  26 , to serve as part of an electrolyte injection path to the inside of the can  11 , is formed on the cap plate  21  and is coupled with a ball  27 . The anode lead  16  is directly connected to the power surface of the cap plate  21  and the cathode lead  17  is electrically coupled to the cathode terminal  23  via the terminal plate  25 . An insulating case  18  is installed on an upper portion of the electrode assembly  12  inside of the can  11  to insulate the electrode assembly  12  from the cap assembly  20 . A lead hole  18   a , which provides an outlet for the cathode lead  17  and an electrolyte liquid inlet hole  18   b , which allows for a flow of the electrolyte liquid therethrough, are formed on the insulating case  18 .  
         [0011]     The prismatic type lithium secondary battery  10 , constructed as described above, therefore includes the jelly roll type electrode assembly  12  inserted inside of the can  11 , the insulating case  18  mounted on the upper surface of the electrode assembly  12 , and the cap assembly  20  mounted on a stage differential member  11   a , which is formed on an upper end of the can  11 .  
         [0012]     The cap assembly  20  is welded to the anode lead at a lower surface of the cap plate  21 . The cathode terminal  23  is welded to the cathode lead. The cap assembly  20  is welded to the can  11  and the electrolyte liquid is injected through the electrolyte liquid injecting hole  26 . The electrolyte liquid injecting hole  26  is then sealed by the ball  27 .  
         [0013]     However, according to the conventional prismatic type lithium secondary battery, the stage differential member  11   a  should be formed to allow for a mounting of the cap assembly  20  on the peripherals of the opening in the upper end of the can  11 . Therefore, a molding process of the stage differential member is required to be added to the process. As such, total production costs of the battery increase, and problems with the mounting of the cap assembly  20  appear.  
         [0014]     Also, according to the conventional prismatic type lithium secondary battery, the insulating case  18 , which is mounted on the upper portion of the electrode assembly, includes an extending part  18   c  to improve sealing properties of the insulating case  18  with the can. As a result, a size of the insulating case is increased and, therefore, a practical capacity of the battery is diminished.  
       SUMMARY OF THE INVENTION  
       [0015]     Accordingly, it is an aspect of the present invention to simplify the process of the can production and to cause a decrease in the cost of the production thereof. Another aspect of the present invention is to relatively easily secure and maintain the proper shape of the cap assembly when the cap assembly is attached to the stage differential member of the can. A further aspect of the present invention is to provide an increased capacity of the battery by simplifying the insulating case of the electrode assembly.  
         [0016]     A prismatic type lithium secondary battery according an embodiment of the present invention includes an electrode assembly including an anode plate, a cathode plate, and a separator wound together; a can to receive the electrode assembly via an opening in an upper end thereof; a cap assembly to seal the opening of the can; an insulating case mounted on an upper portion of the electrode assembly once the electrode assembly is inside the can; and a stopping unit, formed in sides of the can to protrude toward the interior of the can, including a support surface to support the cap assembly and a surface to engage with the insulating case.  
         [0017]     The stopping unit comprises stoppers formed as embossed moldings in opposite sides of the can, each of the stoppers including a support surface.  
         [0018]     The stoppers are formed as circles, prisms, or are streamlined.  
         [0019]     The insulating case comprises a flat plate mounted to be engaged with the lower surface of the stopper.  
         [0020]     The process of the prismatic type lithium secondary battery according to an embodiment of the present invention comprises inserting a jelly roll type electrode assembly into a can; forming a stopper on surfaces of the can above the electrode assembly; mounting an insulating case to an upper portion of the electrode assembly to engage with lower surfaces of the stopper; and mounting a cap assembly on upper surfaces of the stopper  
         [0021]     Thus, the stage differential member of the can is not required. The stopper is formed by compression. As such the process is simplified.  
         [0022]     Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0024]      FIG. 1  is a partial sectional view of a conventional prismatic type lithium secondary battery;  
         [0025]      FIG. 2  is a separated schematic perspective view of a prismatic type lithium secondary battery according to an embodiment of the present invention;  
         [0026]      FIG. 3A  is a plane view of a prismatic type can of  FIG. 2 ;  
         [0027]      FIG. 3B  is a cross-sectional view in along the line A-A of  FIG. 3A ;  
         [0028]      FIG. 4  is a cross-sectional view of the prismatic type lithium secondary battery of  FIG. 2 ;  
         [0029]      FIG. 5A  and  FIG. 5B  are plane views of the prismatic type can of  FIG. 3A ;  
         [0030]      FIG. 6  is a plane view of a prismatic type can according to another embodiment of the present invention 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0031]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0032]     With reference to  FIG. 2 , the prismatic type lithium secondary battery  30 , according to an embodiment of the present invention, includes a can  31 , an electrode assembly  32 , which is received in the can  31 , and a cap assembly  40  coupled to an upper portion of the can  31 . The can  31  is formed with a hollow cavity and is metallic. Therefore, the can  31  may operate as a terminal. A stopper  50  protrudes towards an interior of the can  31  on opposite sides of an upper part of the can  31 .  
         [0033]     The stoppers  50  are each formed as a result of an embossing treatment. The embossing treatment is a form of a compressing process in press processing that can be completed rapidly and with lowered costs.  
         [0034]     Referring now to  FIGS. 3A and 3B , the stopper  50  is shown protruding from opposite surfaces of the can  31  towards the interior of the can  31 . The left and right side stoppers  50  each include an upper surface  50 A and lower surface  50 B. The cap assembly  40  is attached to the can  31  substantially horizontally along the upper surfaces  50 A of each of the stoppers  50 , which provide support for the cap assembly  40 , such that the cap assembly  40  is substantially parallel with a width of the can  31 . Of course, it is understood that the cap assembly  40  need not be attached to the can  31  substantially horizontally and that other formations and arrangements are possible.  
         [0035]     An upper surface of the insulating case  48  is engaged with the lower surface  50 B of each of the stoppers  50 . Therefore, since a size of the left and right side stoppers  50  may be relatively easily controlled by the press treatment system, the can  31  and the stoppers  50  may be formed to have precise respective heights in accordance with a capacity of the battery.  
         [0036]     The electrode assembly  32 , which is received in the interior of the can  31 , includes a cathode plate  33 , an anode plate  35 , and a separator  34 . The cathode plate  33 , the anode plate  35 , and the separator  34  (e.g., a strip or strips of insulating material) are successively laminated and wound into a jelly roll. In accordance with an embodiment of the invention, the separator  34  is plural in number and insulates the cathode plate  33  and the anode plate  35  from one another.  
         [0037]     The cap assembly  40  seals the opening of the can  31  and includes a cap plate  41 . The cap plate  41  is flat and metallic and has a size and shape that corresponds to the opening of the can  31 . A terminal through-hole  42  is formed near a center of the cap plate  41  with a predetermined size. An electrolyte liquid injecting hole  43  is formed on a side of the cap plate  41 . A ball  49  may be used to seal the electrolyte liquid injection hole  43  once an electrolyte has been introduced to the interior of the can  31 .  
         [0038]     A cathode terminal  45  can be inserted through terminal through-hole  42 . A gasket  44 , such as a tube, is installed between an outer surface of the cathode terminal  45  and the through-hole  42  of the cap plate  41 .  
         [0039]     An insulating plate  46  is installed on the lower surface of the cap plate  41 . A terminal plate  47  is installed on lower surface of the insulating plate  46 . Both the insulating plate  46  and the terminal plate  47  include through-holes through which the cathode terminal  45  is inserted. The lower part of the cathode terminal  45  is electrically connected to the terminal plate  47 .  
         [0040]     Since, the insulating case  48  is installed on an upper part of the electrode assembly  32 , the insulating case  48  electrically insulates the cap assembly  40  and the electrode assembly  32  from one another and serves as a flow path for the electrolyte liquid injected through the electrolyte injecting hole  43 . According to an embodiment of the invention, the insulating case  48  comprises high polymer resin, and may include poly-propylene.  
         [0041]     The insulating case  48  installed in close engagement with the lower surface  50 B of the stopper  50  does not require an extending part as in the conventional battery and may be formed as a flat plate. Therefore the shape of the insulating case  48  is relatively simple, and yields space inside of the battery cell such that a capacity of the battery is increased.  
         [0042]     Referring to  FIGS. 2 and 4 , the procedure of the assembly of the prismatic type secondary battery  30  will be described. The cathode plate  33 , the separator  34 , and the anode plate  35  are laminated and wound into a jelly-roll. The wound electrode assembly  32  is then inserted into a can  31 . A pair of embossed stoppers  50  is then formed in the interior of the can  31  by a press treatment using a press machine on the upper end of both side surface portions of the can  31 .  
         [0043]     The insulating case  48  is then mounted on the upper portion of the electrode assembly  32 . The insulating case  48  may be flexible and may be made from poly-propylene etc. Thus, a form of the insulating case  48  may temporarily change when the insulating case  48  is inserted in the can  31 . Because an edge of the insulating case  48  is closely engaged with the lower surface  50 B of the stopper  50 , the insulating case  48  insulates the electrode assembly.  
         [0044]     The cap plate  41  is welded to the can  31 , and the electrolyte liquid is injected into the interior of the can  31 . The electrolyte injection hole  43  is evacuated and sealed with a vacuum sealing device after a predetermined quantity of electrolyte is injected into the can  31 . A cover plug  49  is then welded onto the injection hole  43 .  
         [0045]     The cap plate  41  of the cap assembly  40  is welded onto the upper surfaces  50 A of the left and right side stoppers  50  of the can  31 . As such, the cap assembly  40  and the insulating case  48  are maintained at a constant distance from one another. The anode lead  37  is electrically insulated from the cathode terminal  45 , the cathode lead  36 , and the cathode tab  38 . Conversely, the cathode terminal  45 , the cathode lead  36 , and the cathode tab  38  remain electrically connected.  
         [0046]      FIGS. 5A and 5B  are plane views of the prismatic type can of  FIG. 3A . As shown in  FIG. 5A , the stoppers  50  are formed as half-circles  51  protruding towards an interior of the can  31 . Meanwhile, as shown in  FIG. 5B , the stoppers  50  are formed as rectangular shapes  52  protruding towards an interior of the can  31 . According to additional embodiments of the invention, the stoppers  50  may be any shape that provides support for both the cap assembly  40  and the insulating case  48 .  
         [0047]      FIG. 6  is a plane view of the can  31  according to another embodiment of the present invention. Here, the stoppers  50  are formed on an inside of the both of the shorter sides of the can  31  and additional stoppers  50  are formed in the longer sides of the can  31 . Thus, the supporting area, which supports the cap assembly  40 , is broadened by the additionally formed stoppers  50 . Therefore the supporting of the cap assembly  40  is additionally stabilized.  
         [0048]     As is described above, a prismatic type lithium secondary battery according to aspects of the present invention may lead to a decrease in production costs by simplifying the molding process of the receiving portion of the cap assembly, results in the cap assembly being shaped and leveled appropriately, and provides for an increased capacity of the battery.  
         [0049]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.