Patent Publication Number: US-2013230764-A1

Title: Method of manufacturing header for lithium battery using polymer and header for lithium battery manufactured by the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119 of Korean Patent Application No. 10-2012-0021644, filed on Mar. 2, 2012 in the Korean Intellectual Property Office, the entirety of which disclosure is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to lithium batteries, and more particularly, to a method of manufacturing a header for lithium batteries more simply than a glass fusion bonding method, and a header for lithium batteries manufactured by the same. 
     2. Description of the Related Art 
     A lithium battery refers to a battery that uses a lithium component such as lithium or a lithium alloy as an anode material. 
     Such lithium batteries have higher power and higher capacity than existing manganese batteries and are widely used as power sources for various electronic appliances. 
       FIG. 1  schematically shows a general lithium battery. 
     Referring to  FIG. 1 , a lithium battery includes a case  110  open at top thereof, an anode  120 , a separator  130 , a cathode  140 , and a header. 
     The anode  120  is placed inside the case  110  and includes a lithium component. 
     The separator  130  is disposed inside the anode  120  and separates the anode  120  from the cathode  140 . 
     The cathode  140  is disposed inside the separator  130  and includes a current collector  145  and a cathode active material. 
     The header covers the top of the header. The header includes a body  150   a  serving as an anode terminal, a cathode pin  150   b  serving as a cathode terminal, and an insulator  150   c  electrically insulating the body  150   a  from the cathode pin  150   b.  Generally, the body  150   a  is connected to the anode through the case  110 . The anode pin  150   b  is connected to the current collector  145  of the cathode  140  through a lead wire  160 . 
     An insulating plate  170  insulates the header from elements inside the case. The insulating plate  170  may be made of fluorinated ethylene propylene (FEP) or the like. 
       FIG. 2  shows a general header structure for lithium batteries, and  FIG. 3  is a plan view of the header shown in  FIG. 2 . 
     Referring to  FIGS. 2 and 3 , the header for lithium batteries includes a body  210  defining a hole therein, a cathode pin  220  placed in the hole, and an insulator  230  holding the cathode pin  220  while electrically insulating the body  210  from the cathode pin  220 . 
     The body  210  is coupled to the case  110  (see  FIG. 1 ) and may serve as an anode terminal The cathode pin  220  is electrically connected to the current collector  145  (see  FIG. 1 ) of the cathode. The body  210  and the cathode pin  220  are made of metal. 
     For operation of the lithium battery, the body  210  and the cathode pin  220  must be electrically insulated from each other. For this reason, the insulator  230  is formed between the body  210  and the cathode pin  220 . Also, the insulator  230  serves not only to seal the interior of the lithium battery, but also to hold the cathode pin  220 . 
     The insulator  230  is generally formed by a glass fusion bonding method. 
     However, the glass fusion bonding method includes a glass melting process and a glass cooling process, and thus requires long time to manufacture the header, thereby lowering productivity. 
     Korean Patent Publication No. 10-2011-0106506 (published on Sep. 29, 2011) discloses such a conventional header for lithium batteries, which is formed through glass fusion bonding. 
     BRIEF SUMMARY 
     The present invention provides a method of manufacturing a header for lithium batteries, which may shorten a manufacturing time as compared with a glass fusion bonding method. 
     In addition, the present invention provides a header for lithium batteries manufactured by the foregoing method. 
     Further, the present invention provides a lithium battery including the header. 
     In accordance with one aspect of the present invention, a method of manufacturing a header for lithium batteries includes: securing a body having a hole inside dies, and securing a cathode pin in the hole so as not to contact the body; filling the hole with polymer powder; and heating the dies to melt the polymer powder, followed by cooling and curing the melted polymer. 
     In accordance with another aspect of the present invention, a method of manufacturing a header for lithium batteries includes: securing a body having a hole inside dies, and securing a cathode pin in the hole so as not to contact the body; filling the hole with a liquid polymer; and curing the polymer filling the hole. 
     In accordance with a further aspect of the present invention, a header for lithium batteries includes: a body having a hole; a cathode pin formed inside the hole and separated from the body; and an insulator formed of a polymer within the hole and electrically insulating the body from the cathode pin. 
     In accordance with yet another aspect of the present invention, a lithium battery includes: a case open at a top thereof; an anode disposed on an inner wall of the case and containing a lithium component; a separator disposed inside the anode; a cathode disposed inside the separator; an electrolyte filling the case; and a header coupled to the top of the case and electrically connected to the anode and the cathode, the header comprising: a body having a hole and electrically connected to the anode; a cathode pin formed inside the hole to be separated from the body and electrically connected to the cathode; and an insulator formed of a polymer within the hole and electrically insulating the body from the cathode pin. 
     The header may be coupled to the case by laser welding. 
     According to the present invention, the method of manufacturing a header for lithium batteries uses a polymer, so that it can be easier and take less time to manufacture the header for lithium batteries than the conventional glass fusion bonding method. 
     In addition, the manufactured header is coupled to a case of a lithium battery by laser welding, thereby providing improved sealing effects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the invention will become apparent from the detailed description of the following embodiments in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view of a general lithium battery; 
         FIG. 2  shows a general header structure for the lithium battery; 
         FIG. 3  is a plan view of the header for lithium batteries shown in  FIG. 2 ; 
         FIG. 4  shows a method of manufacturing a header for lithium batteries in accordance with one embodiment of the present invention, which uses polymer powder; 
         FIG. 5  shows a method of manufacturing a header for lithium batteries in accordance with another embodiment of the present invention, which uses a liquid polymer; and 
         FIG. 6  shows a header structure in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention will now be described in detail with reference to the accompanying drawings. It should be understood that the present invention is not limited to the following embodiments and may be embodied in different ways, and that the embodiments are given to provide complete disclosure of the invention and to provide thorough understanding of the invention to those skilled in the art. The scope of the invention is limited only by the accompanying claims and equivalents thereof. Like components will be denoted by like reference numerals throughout the specification. 
     Now, a method of manufacturing a header for lithium batteries using polymer in accordance with the present invention and a header for lithium batteries manufactured by the method will be described with reference to the accompanying drawings. 
       FIG. 4  shows a method of manufacturing a header for lithium batteries in accordance with one embodiment of the present invention. 
     Referring to  FIG. 4 , the method of manufacturing a header for lithium batteries includes securing a body/cathode pin in S 410 , filling polymer powder in S 420 , and melting/curing the polymer in S 430 . 
     In operation S 410  of securing a body/cathode pin, a body having a hole is secured inside dies and a cathode pin is secured inside the hole so as not to contact the body. 
     The body may be previously manufactured in a header shape, or may be formed to have a header shape by the dies. 
     Next, in operation S 420  of filling a polymer powder, the hole is filled with the polymer powder. 
     The polymer may include butyl rubbers, silicon rubbers or butadiene rubbers, which exhibit excellent properties in terms of strength and sealing properties, without being limited thereto as long as the polymer has insulation properties. 
     To enhance sealing and coupling properties, the polymer powder may be provided not only to the hole, but also to a space between the dies and parts of the top and bottom of the body. 
     Next, in operation S 430  of melting/curing the polymer, the polymer inside the hole is melted by heating the dies, and cooled and cured. At this time, the curing process may include a drying process. 
     When these operations described above are completed, the header for lithium batteries as shown in  FIG. 6  may be provided. 
     Although the method illustrated as using the polymer powder in  FIG. 4 , a liquid polymer may be used instead of the polymer powder. 
       FIG. 5  shows a method of manufacturing a header for lithium batteries in accordance with another embodiment of the present invention, which uses a liquid polymer. 
     Referring to  FIG. 5 , the method of manufacturing a header for lithium batteries includes securing a body/cathode pin in S 510 , injecting a liquid polymer in S 520 , and curing the polymer in S 530 . 
     In operation S 510  of securing a body/cathode pin, a body having a hole is secured inside dies, and a cathode pin is secured inside the hole so as not to contact the body. The body may be previously subjected to a masking process except for a region corresponding to the interior of the hole which will receive the liquid polymer. 
     Next, in operation S 520  of injecting a liquid polymer, the liquid polymer is injected into the dies such that the hole is filled with the liquid polymer. 
     Here, the liquid polymer may be a polymer in a liquid state, or a polymer containing solution. 
     To enhance sealing and coupling properties, the liquid polymer may be provided not only to the hole, but also to a space between the dies and parts of the top and bottom of the body. 
     Next, in operation S 530  of curing the polymer, the polymer inside the hole is hardened. At this time, curing may include a drying process. 
     Curing may be determined in accordance with the kinds of polymer. For example, in order to cure the polymer, heating may be applied to thermosetting polymers, and ultraviolet light may be applied to UV-setting polymers. 
     When these operations described above are completed, the header for lithium batteries as shown in  FIG. 6  may be provided. 
       FIG. 6  shows a header structure in accordance with one embodiment of the present invention. 
     Referring to  FIG. 6 , the header for lithium batteries includes a body  510 , a cathode pin  520 , and an insulator  530 . 
     In the header for lithium batteries, the body  510  covers the top of a case and functions as an anode terminal The body  510  may be made of a material such as stainless steel, which exhibits excellent properties in terms of durability and conductivity. 
     The body  510  is formed with a hole for forming the cathode pin  520 . 
     The cathode pin  520  is formed inside the hole to be separated from the body  510 . In the header, the cathode pin  520  functions as a cathode terminal and may also be made of a material such as stainless steel, which exhibits excellent properties in terms of durability and conductivity. 
     The insulator  530  is made of a polymer within the hole. The insulator  530  electrically insulates the body  510  from the cathode pin  520 . Further, the insulator  530  holds the cathode pin  520  and seals the hole. Accordingly, the insulator may be composed of butyl rubbers, silicon rubbers or butadiene rubbers, which exhibit excellent properties in terms of strength and sealing properties. 
     The body  510  may be partially provided at the top and bottom thereof with the insulator  530 , as shown in  FIG. 6 . In this case, coupling and sealing properties may be further improved with increasing coupling area between the insulator  530  and the body  510 . 
     The header according to the present invention may be used for a lithium battery as shown in  FIG. 1 . 
     In this case, the lithium battery in accordance with the present invention includes a case  110 , a cathode  120 , a separator  130 , an anode  140 , an electrolyte (not shown), and the header. 
     The case  110  is made of stainless steel or the like, and is open at the top thereof. The anode  120  is disposed on an inner wall of the case  110  and contains a lithium component. The separator  130  is disposed inside the anode  120 . The cathode  140  is disposed inside the separator  130 . The electrolyte (not shown) fills the case. The header is coupled to the top of the case  110  and is electrically connected to the anode  120  and the cathode  140 . 
     The header according to the present invention includes the body  510 , the cathode pin  520 , and the insulator  530 . The insulator  530  for electrically insulating the body  510  from the cathode pin  520  may be formed of a polymer and formed by injection molding. 
     In  FIG. 1 , part “A” shows a coupling part between the header and the case. The header may be coupled to the case  110  by laser welding. 
     Conventionally, press-fitting or gasket-insertion between the header and the case is used for sealing the battery when coupling the header and the case. However, such a conventional battery provides unsatisfactory sealing-properties. 
     On the other hand, when the header and the case are coupled to each other by laser welding, the battery has good sealing-properties. Therefore, it is desirable that the header be coupled to the case by laser welding. 
     As described above, the method of manufacturing the header for lithium batteries in accordance with the present invention uses injection-molding of a polymer, so that it can be easier and take less time to manufacture the header for lithium batteries than the conventional glass fusion bonding method. Also, the manufactured header is coupled to the case by laser welding, thereby providing improved sealing effects. 
     Although some embodiments have been described herein, it should be understood by those skilled in the art that these embodiments are given by way of illustration only, and that various modifications, variations, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be limited only by the accompanying claims and equivalents thereof.