Abstract:
A rechargeable battery and a method of assembling the rechargeable battery. The method includes the steps of: accommodating an electrode assembly into a case, the electrode assembly having first and second electrode taps protruding therefrom; forcibly inserting an electrode terminal into an insulating gasket, the insulating gasket having an inner diameter smaller than an outer diameter of the electrode terminal; forcibly inserting the insulating gasket into a terminal hole in a cap plate of a cap assembly; and sealing the case with the cap assembly. Accordingly, it is possible to increase a sealing force between the case and the cap assembly and effectively insulate the electrode terminal from the cap plate.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
       [0001]     This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0019836, filed on Mar. 9, 2005, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a rechargeable battery, and, more particularly, to a rechargeable battery having a cap assembly covering a case accommodating an electrode assembly.  
         [0004]     2. Description of Related Art  
         [0005]     Recently, a large number of compact and lightweight electric or electronic apparatuses such as cellular phones, notebooks, and camcorders have been actively developed and produced. These portable electric or electronic apparatuses are provided with battery packs, so that these apparatuses can operate without separate power supplies. A battery pack includes at least one battery for outputting a voltage having a predetermined level to drive a portable electric or electronic apparatus for a predetermined time.  
         [0006]     Recently, for economical efficiency reasons, a battery pack has employed a rechargeable battery. A nickel cadmium (Ni—Cd) battery, a nickel hydride (Ni-MH) battery, and a lithium rechargeable battery, such as a lithium (Li) polymer battery and a Lithium ion (Li-ion) battery, are all representative examples of rechargeable batteries.  
         [0007]     Particularly, the lithium rechargeable battery has an operating voltage of 3.6V, which is three times higher than that of the Ni—Cd battery or the Ni-MH battery. In addition, the lithium rechargeable battery has a high energy density per unit weight. Therefore, the demands for the lithium rechargeable battery have been rapidly increased.  
         [0008]     For the lithium rechargeable battery, a lithium-based oxide is used as a positive electrode active material, and carbon is used as a negative electrode active material. In general, batteries are classified into a liquid electrolyte battery and a polymer electrolyte battery according to a type of the electrolyte. The lithium rechargeable battery using the liquid electrolyte is referred to as a lithium ion battery, and the lithium rechargeable battery using the polymer electrolyte is referred to as a lithium polymer battery. The lithium rechargeable batteries are manufactured in various shapes. According to the shapes, the lithium rechargeable batteries are classified into a can-type battery, a prismatic battery, and a pouch-type battery.  
         [0009]     In general, a lithium rechargeable battery is constructed with a case, a jelly-roll-type electrode assembly accommodated into the case, and a cap assembly covering the upper portion of the case.  
         [0010]     The electrode assembly is constructed by rolling a positive electrode plate coated with a positive electrode active material, a negative electrode plate coated with a negative electrode active material, and a separator interposed between the positive and negative electrode plates to prevent short circuit between the two electrode plates and to allow only lithium ions (Li-ions) to pass through. In addition, an electrolyte solution is contained in the case to enable the lithium ions to move.  
         [0011]     The cap assembly is engaged with the upper opening of the case where the electrode assembly is accommodated. The cap assembly includes a plate-shaped cap plate having the same size and shape as those of the opening of the case. A central portion of the cap plate is provided with a terminal hole through which an electrode terminal passes.  
         [0012]     A tube-shaped gasket is provided to surround the outside of the electrode terminal in order to electrically insulate the electrode terminal from the cap plate. An insulating plate is disposed on a bottom surface of the cap plate, and a terminal plate connected to the electrode terminal is disposed on a bottom surface of the insulating plate.  
         [0013]     The electrode assembly is accommodated into the case and fixed so as not to be detached. The electrolyte solution is injected into the case, and then the opening of the case is sealed with the cap assembly to form the complete lithium rechargeable battery.  
         [0014]     In the aforementioned lithium rechargeable battery, since the electrode terminal is formed to protrude through the terminal hole formed on the cap plate, the tube-shaped gasket is inserted into the terminal hole to prevent contact between the electrode terminal and the cap plate.  
         [0015]     However, in the conventional cap assembly, gaps may occur among the assembled portions of the electrode terminal, the gasket surrounding the electrode terminal, and the terminal hole of the cap plate.  
         [0016]     In addition, the electrolyte solution contained in the case may leak out through the gaps of the assembled portions.  
       SUMMARY OF THE INVENTION  
       [0017]     Embodiments of the present invention provide a rechargeable battery having a cap assembly capable of increasing a sealing force of a cap plate, a gasket, and an electrode terminal; and/or a method of assembling the rechargeable battery.  
         [0018]     An embodiment of the present invention provides a method of assembling a rechargeable battery. The method includes the steps of: accommodating an electrode assembly into a case, the electrode assembly having first and second electrode taps protruding therefrom; forcibly inserting an electrode terminal into an insulating gasket, the insulating gasket having an inner diameter not greater than an outer diameter of the electrode terminal; forcibly inserting the insulating gasket into a terminal hole of a cap assembly; and sealing the case with the cap assembly.  
         [0019]     In one embodiment of the present invention, the outer diameter of the electrode terminal is formed to be larger than the inner diameter of the insulating gasket. In addition, the inner diameter of the insulating gasket may be about 96% to 97% of the outer diameter of the electrode terminal.  
         [0020]     In addition, the outer diameter of the insulating gasket may be formed to be larger than the inner diameter of the terminal hole. In addition, the inner diameter of the terminal hole may be about 96% to 97% of the outer diameter of the insulating gasket.  
         [0021]     In addition, the electrode terminal may be a negative electrode.  
         [0022]     Another embodiment of the present invention provides a rechargeable battery including: an electrode assembly having two electrodes and a separator interposed between the two electrodes to prevent short circuit between the two electrodes; a case (e.g., a can) having an opening through which the electrode assembly is accommodated; and a cap assembly covering the can, the cap assembly having a plate-shaped cap plate on which a terminal hole is formed, a tube-shaped insulating gasket inserted into the terminal hole, and an electrode terminal passing through the insulating gasket, wherein the electrode terminal is forcibly inserted into the insulating gasket, and the insulating gasket is forcibly inserted into the terminal hole of the cap plate.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention.  
         [0024]      FIG. 1  is a perspective exploded view showing a rechargeable battery according to an embodiment of the present invention;  
         [0025]      FIG. 2  is a view showing an assembling relation of parts of the rechargeable battery according to the embodiment of the present invention;  
         [0026]      FIG. 3  is a cross-sectional view showing of the rechargeable battery according to the embodiment of the present invention; and  
         [0027]      FIG. 4  is a flowchart showing processes of assembling the rechargeable battery according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0028]     In the following detailed description, certain exemplary embodiments of the present invention are shown and described, by way of illustration. As those skilled in the art would recognize, the described exemplary embodiments may be modified in various ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, rather than restrictive.  
         [0029]     Now, a rechargeable battery according to an embodiment of the present invention will be described in more detail with reference to  FIGS. 1, 2 , and  3 .  
         [0030]      FIG. 1  is a perspective exploded view showing a rechargeable battery according to the embodiment of the present invention.  FIG. 2  is a view showing an assembling relation of parts of the rechargeable battery according to the embodiment of the present invention.  FIG. 3  is a cross-sectional view showing of the rechargeable battery according to the embodiment of the present invention. As shown in FIGS.  1  to  3 , the rechargeable battery includes a case  200  having an opening  201  at one side thereof, an electrode assembly  250  which is accommodated into the case  200 , and a cap assembly  100  which is engaged with the opening  201  to seal an upper portion of the case  200 .  
         [0031]     In the embodiment, the case  200  has a shape of a rectangular box and is made of aluminum or an aluminum alloy. The electrode assembly  250  and an electrolyte solution are accommodated into the case  200  through the opening  201  thereof. The case  200  may also function as one of a first electrode  210  and a second electrode  220 .  
         [0032]     The electrode assembly  250  is formed to have a shape of a thin plate or a film. In order to form the electrode assembly  250 , a stacked structure is first constructed by stacking the first electrode  210  connected to a first electrode tap  215 , a separator  230 , and the second electrode  220  connected to a second tap  225 , and then the stacked structure is rolled into a shape of a roll. The first electrode  210  or the second electrode  220  may be one of a positive electrode or a negative electrode. In one embodiment, the first electrode  210  is the negative electrode.  
         [0033]     The negative electrode includes a negative current collector constructed with a conductive metal thin film such as a copper foil and negative active material layers coated on both sides thereof. The negative active material layers are substantially made of carbon. In the negative electrode, a negative electrode tap is disposed in a plate region of the negative current collector where the negative electrode active material layers are not formed, and the negative electrode tap protrudes upwardly.  
         [0034]     The positive electrode includes a positive current collector constructed with a highly conductive metal thin film such as an aluminum foil and positive electrode material active layers coated on both side thereof. The positive electrode material active layers are substantially made of a lithium oxide. In the positive electrode, a positive electrode tap is electrically connected to a plate region of the positive current collector where the positive electrode active material layers are not formed, and the positive electrode tap protrudes upwardly.  
         [0035]     The separator  230  is made of polyethylene, polypropylene, or a co-polymer thereof. The separator  230  has a width wider than those of the first and second electrodes  210  and  220  in order to effectively prevent short circuit between the two electrodes  210  and  220  (or the two electrode plates).  
         [0036]     The cap assembly  100  covers the opening  201  of the case  200  to seal the case  200 . The cap assembly  100  is provided with a plate-shaped cap plate  110  having the same size and shape as those of the opening  201  of the case  200 . A bottom surface of the cap plate  110  is provided with an insulating plate  140 . The insulating plate  140  is provided with a terminal plate  150  which is electrically connected to the first electrode tap  215  disposed on the first electrode  210 .  
         [0037]     A central portion of the cap plate  110  is provided with a first terminal hole  111  through which an electrode terminal  130  passes to connect to the first electrode tap  215 . The first terminal hole  111  is provided with an insulating gasket  120  having a shape of a tube in order to electrically insulate the electrode terminal  130  from the cap plate  110 .  
         [0038]     An outer diameter A of the electrode terminal  130  inserted into the insulating gasket  120  is formed to be larger than an inner diameter B of the insulating gasket  120 . In one embodiment, the inner diameter B of the insulating gasket  120  is about 96% to 97% of the outer diameter A of the electrode terminal  130 .  
         [0039]     In addition, an inner diameter D of the first terminal hole  111  is formed to be smaller than an outer diameter C of the insulating gasket  120 . In one embodiment, the inner diameter D of the first terminal hole  111  is about 96% to 97% of the outer diameter C of the insulating gasket  120 .  
         [0040]     For example, in one embodiment, if the outer diameter A of the electrode terminal  130  is Φ1.25, the inner diameter B of the insulating gasket  120  is (P1.2, which is smaller than Φ1.25. Also, in one embodiment, if the outer diameter C of the insulating gasket  120  is Φ1.5, inner diameter D of the first terminal hole  111  is Φ1.45, which is smaller than Φ1.5.  
         [0041]     Therefore, the electrode terminal  130  can be forcibly inserted (or can be pressure fitted) into the insulating gasket  120 , and the insulating gasket  120  into which the electrode terminal  130  is inserted can be forcibly inserted (or can be pressure fitted) into the first terminal hole  111  of the cap plate  110 .  
         [0042]     Here, the aforementioned sizes of the gasket, the terminal hole, and the electrode terminal are value set before the assembling of the cap plate, the gasket, and the electrode terminal. That is, the aforementioned sizes thereof are values before the deformation thereof. Therefore, the inner diameter of the gasket is set to be equal to or less than the outer diameter of the electrode terminal, and the inner diameter of the terminal hole is set to be equal to or less than the outer diameter of the gasket.  
         [0043]     The insulating gasket is made of a material having a mechanical strength, a sealing property, and a chemical resistance to an electrolyte solution. For example, the material includes a fluorinate resin such as perfluoroalkoxy (PFA) and a fluorinate ethylene propylene (FEP) copolymer, and a crystalline polymer resin such as polypropylene (PP) and polyethylene terephthalate (PET).  
         [0044]     In addition, an electrolyte solution injection hole  113  having a predetermined size is provided at around one side of the cap plate  110 . After the cap assembly  100  is engaged with the opening  201  of the case  220 , an electrolyte solution is injected through the electrolyte solution injection hole  113 . After that, the electrolyte solution injection hole  113  is blocked (or clogged) with a stopper  115 .  
         [0045]     The insulating plate  140  made of an insulating material is disposed on a bottom surface of the cap plate  110 . The insulating plate  140  is provided with a second terminal hole  141 . The second terminal hole  141  is formed to correspond to the first terminal hole  111  of the cap plate  110  and is connected to the first terminal hole  111 .  
         [0046]     The terminal plate  150  is made of Ni or a Ni alloy. The terminal plate  150  is disposed on a bottom surface of the insulating plate  140 . The terminal plate  150  is provided with a third terminal hole  151 . The third terminal hole  151  is formed to correspond to the first terminal hole  111 .  
         [0047]     An insulating case  160  is disposed over the upper portion of the electrode assembly  250  to insulate the electrode assembly  250  from the cap plate  110 . The insulating case  160  is made of an insulating polymer resin. In one embodiment, the insulating case  160  is made of polypropylene. However, the present invention is not limited thereto.  
         [0048]     The insulating case  160  is provided with first and second electrode tap insert holes  163  and  165  through which the first and second electrode taps  215  and  225  protruding upwardly from the electrode assembly  250  pass and an electrolyte solution injection hole  161  through which the electrolyte solution injected through the electrolyte solution injection hole  113  of the cap plate  110  is injected.  
         [0049]     Now, processes of assembling the aforementioned rechargeable battery according to an embodiment of the present invention will be described in more detail with reference to  FIG. 4 .  
         [0050]     Firstly, the electrode assembly  250  constructed by rolling the first and second electrodes  210  and  220  and the separator  230  (into the shape of the roll) is accommodated into the case  220  (S 500 ).  
         [0051]     Next, the electrode terminal  130  is inserted into the tube-shaped insulating gasket  120 . The inner diameter B of the insulating gasket  120  is formed to be about 96% to 97% of the outer diameter A of the electrode terminal  130 . In one embodiment, since the outer diameter A of the electrode terminal  130  is formed to be larger than the inner diameter B of the insulating gasket  120 , the electrode terminal  103  is forcibly inserted into the insulating gasket  120  by rotating and pressing the electrode terminal  130  (S 510 )  
         [0052]     Next, the insulating gasket  120  into which the electrode terminal  130  is forcibly inserted is inserted into the first terminal hole  111  of the cap plate  110 . The inner diameter D of the first terminal hole  111  is about 96% to 97% of the outer diameter C of the insulating gasket  120 . In one embodiment, since the outer diameter of the insulating gasket  120  is formed to be larger than the inner diameter D of the first terminal hole  111 , the insulating gasket  120  is forcibly inserted into the cap plate  110  by rotating and pressing the insulating gasket  120  similar to the electrode terminal  130  (S 520 )  
         [0053]     Next, the insulating plate  140  and the terminal plate  150  are sequentially disposed on the bottom surface of the cap plate  110 . The electrode terminal  130  forcibly inserted into the first terminal hole  111  is sequentially inserted into the second terminal hole  141  of the insulating plate  140  and the third terminal hole  151  of the terminal plate  150 .  
         [0054]     Since the electrode terminal  130  is insulated from the cap plate  110  by the insulating gasket  120  and engaged with the first terminal hole  111  of the cap plate  110 , the terminal plate  150  is electrically insulated from the cap plate  110  and electrically connected to the electrode terminal  130 .  
         [0055]     Next, the insulating case  160  is disposed over the upper portion of the electrode assembly  250  to electrically insulate the electrode assembly  250  from the cap assembly  100  and to cover the upper portion of the electrode assembly  250 . The first and second electrode taps  215  and  225  protrude through the first and second electrode tap insert holes  163  and  165  of the insulating case  160 .  
         [0056]     Next, the cap assembly  100  is disposed on the opening  201  of the case  200 . The first electrode tap  215  is connected to the terminal plate  150  of the electrode terminal  130 , and the second electrode tap  225  is connected to the cap plate  110 .  
         [0057]     According to the present invention, in a cap assembly of a rechargeable battery, an electrode terminal and an insulating gasket are forcibly inserted into a cap plate, thereby increasing a sealing force between a case and the cap assembly and effectively insulate the electrode terminal from the cap plate.  
         [0058]     While the invention has been described in connection with certain exemplary embodiments, it is to be understood by those skilled in the art that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications included within the spirit and scope of the appended claims and equivalents thereof.