Abstract:
A secondary battery includes: a case; an electrode assembly housed in the case and including a first electrode, a second electrode, and a separator between the first electrode and the second electrode, the first electrode having a coating portion coated with a first active material and a non-coating portion absent the first active material; and a collector plate including first and second collector plates enmeshed together with the non-coating portion therebetween.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/346,299, filed on May 19, 2010, in the United States Patent and Trademark Office, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Aspects of embodiments of the present invention relate to a secondary battery. 
     2. Related Art 
     In general, unlike primary batteries, which are not chargeable, secondary batteries are chargeable and dischargeable. The secondary batteries, in particular, small size batteries, are widely used in a variety of high-tech electronic devices such as cellular phones, notebook computers, camcorders, and the like, and bulk size (e.g., large size) batteries are used as the power source for motor drive, such as in electric vehicles or hybrid electric vehicles. The secondary battery is generally constructed to include an electrode assembly inside a case and electrode terminals connected through a collector plate welded to the electrode assembly. However, in some secondary batteries it is difficult to check welding quality from the outside and therefore welding efficiency may deteriorate. 
     SUMMARY 
     Aspects of embodiments of the present invention are directed toward a secondary battery in which welding efficiency and reliability are improved when a non-coating portion of an electrode assembly is welded to a collector plate and in which welding quality can be easily detected. 
     According to one embodiment of the present invention, a secondary battery includes: a case; an electrode assembly housed in the case and including a first electrode, a second electrode, and a separator between the first electrode and the second electrode, the first electrode having a coating portion coated with a first active material and a non-coating portion absent the first active material; and a collector plate including first and second collector plates enmeshed together with the non-coating portion therebetween. 
     The first collector plate may include a first plate and a first protrusion extending from the first plate with a first step height from the first plate, and the second collector plate may include a second plate and a second protrusion extending from the second plate with a second step height from the second plate. 
     The non-coating portion may be between the first protrusion and the second protrusion. 
     The non-coating portion may be coupled to both the first protrusion and the second protrusion by a weld between the first and second protrusions. 
     The weld may be a butt weld. 
     The weld may be at an end of the non-coating portion. 
     The non-coating portion may extend from the coating portion with a distance greater than the first step height or the second step height. 
     The non-coating portion may be welded to the collector plate in a state in which an end of the non-coating portion is coplanar with the collector plate. 
     The non-coating portion may be welded to the collector plate in a state in which an end of the non-coating portion extends through the collector plate. 
     The first collector plate may include a plurality of first protrusions, the second collector plate may include a plurality of second protrusions enmeshed with the plurality of first protrusions, and one of the plurality of first protrusions and a corresponding one of the plurality of second protrusions may be enmeshed together with the non-coating portion therebetween. 
     The first electrode may be wound together with the second electrode and the separator to form a jellyroll structure, and the jellyroll structure may include the non-coating portion, the non-coating portion located at a first end of the electrode assembly and between the enmeshed first and second collector plates. 
     The first collector plate may include a first plate and a plurality of first protrusions extending from the first plate with a first step height from the first plate. 
     The first plate may have a surface abutting the first end of the electrode assembly, and the plurality of first protrusions may be located within the non-coating portion. 
     The plurality of first protrusions may define a plurality of grooves, and the non-coating portion may include a plurality of portions partitioned by and located in the plurality of grooves. 
     The second collector plate may include a second plate and a plurality of second protrusions extending from the second plate with a second step height from the second plate. 
     The first plate may have a surface abutting the first end of the electrode assembly, the plurality of first protrusions may be located within the non-coating portion, the second plate may have a surface abutting the first end of the electrode assembly, and the plurality of second protrusions may be located within the non-coating portion. 
     The plurality of first protrusions may define a plurality of first grooves, the non-coating portion may include a plurality of portions first partitioned by and located in the plurality of first grooves, the plurality of second protrusions may define a plurality of second grooves, and the plurality of portions may be second partitioned by and located in the plurality of second grooves. 
     The non-coating portion may include a first set of non-coating portions and a second set of non-coating portions, the first set of the non-coating portions may be located between a first one of the plurality of first protrusions and a corresponding first one of the plurality of second protrusions, and the second set of the non-coating portions may be located between a second one of the plurality of first protrusions and a corresponding second one of the plurality of second protrusions. 
     The first set of the non-coating portions may be welded to both the first one of the plurality of first protrusions and the corresponding first one of the plurality of second protrusions by a first weld, and the second set of the non-coating portions may be welded to both the second one of the plurality of first protrusions and the corresponding second one of the plurality of second protrusions by a second weld. 
     The first weld and the second weld may together form a serpentine weld. 
     In secondary batteries according to embodiments of the present invention, in welding a collector plate to a non-coating portion of an electrode assembly, butt welding is performed in a state in which the non-coating portion is fixed between protrusions of a first collector plate and a second collector plate meshed with each other, thereby increasing welding efficiency. 
     In addition, in secondary batteries according to embodiments of the present invention, because welding is performed on lateral surfaces of the non-coating portion, welding quality can be easily detected externally, thereby improving welding reliability. 
     Further, secondary batteries according to embodiments of the present invention can increase the capacity of the electrode assembly by reducing a thickness of the non-coating portion by as much as a step height between the first collector plate and the second collector plate. 
     Additional aspects of embodiments of the present 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 
         FIG. 1  is an exploded perspective view of a secondary battery according to one embodiment of the present invention; 
         FIG. 2  is an enlarged view of a portion ‘A’ of  FIG. 1  according to one embodiment of the present invention; 
         FIG. 3  is a front view of a first collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 4  is a side view of a first collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 5  is a front view of a second collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 6  is a side view of a second collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention; and 
         FIGS. 7 and 8  illustrate a procedure in which a collector plate and a non-coating portion are coupled to each other in a secondary battery according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SOME OF THE SYMBOLS IN CERTAIN PORTIONS OF THE DRAWINGS 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 100: Secondary Battery 
                 110: Case 
               
               
                   
                 120: Electrode Assembly 
                 130: Collector Plate 
               
               
                   
                 140: Current Collecting Terminal 
                 150: First Dielectric 
               
               
                   
                 160: Cap plate 
                 170: Second Dielectric 
               
               
                   
                 180: Nut 
               
               
                   
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION 
     Example embodiments will now be described in more detail hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     A construction of a secondary battery according to one embodiment of the present invention will now be described. 
       FIG. 1  is an exploded perspective view of a secondary battery according to one embodiment of the present invention,  FIG. 2  is an enlarged view of a portion ‘A’ of  FIG. 1  according to one embodiment of the present invention,  FIG. 3  is a front view of a first collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention,  FIG. 4  is a side view of a first collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention,  FIG. 5  is a front view of a second collector plate used in the secondary battery shown in  FIG. 1  according to one embodiment of the present invention, and  FIG. 6  is a side view of the second collector plate used in the secondary battery shown in  FIG. 1 , according to one embodiment of the present invention. 
     Referring to  FIGS. 1 through 6 , a secondary battery  100  according to one embodiment of the present invention includes a case  110 , an electrode assembly  120  housed inside the case  110 , a collector plate  130  electrically connected to the electrode assembly  120 , a current collecting terminal  140  electrically connected to the collector plate  130 , a first dielectric  150  through which the current collecting terminal  140  penetrates, a cap plate  160  coupled to an upper side of the first dielectric  150 , and a second dielectric  170  penetrating through the cap plate  160  and coupled to the current collecting terminal  140 . A nut  180  may further be coupled to the current collecting terminal  140 . 
     The case  110  may have the shape of a hexahedron (e.g., rectangular prism) or shapes having an inner space to receive (e.g., to contain) the electrode assembly  120 . In addition, the case  110  is made of conductive metal, for example, steel coated with aluminum, aluminum alloy or nickel. 
     The electrode assembly  120  is housed inside the case  110 . The electrode assembly  120  is constructed such that a separator  123  is located between a positive electrode  121  and a negative electrode  122 . In a state in which the positive electrode  121 , the separator  123  and the negative electrode  122  are stacked, the electrode assembly  120  is formed to have a jellyroll shape in which the stacked structure in which the positive electrode  121 , the separator  123  and the negative electrode  122  are wound together into a jellyroll configuration. In the embodiment shown in  FIG. 1 , for brevity of explanation, only a single electrode assembly  120  is provided inside the case  110 , but it should be understood that a plurality of electrode assemblies  120  may be provided inside the case  110 . 
     In addition, the electrode assembly  120  includes a non-coating portion  124  (or uncoated portion) at either end of the case  110 . The non-coating portion  124  is formed in pair, that is, a first portion of the non-coating portion  124  is formed at a first end of the electrode assembly  120  to be connected to the positive electrode plate  121 , and a second portion of the non-coating portion  124  is formed at a second end of the electrode assembly  120  to be connected to the negative electrode plate  122 . 
     The non-coating portion  124  is arranged to correspond to the shape of the collector plate  130  and to be coupled to the collector plate  130 . The non-coating portion  124  may be coupled to the collector plate  130  by welding in a state in which it is coplanar with the collector plate  130  or in which it upwardly protrudes from the collector plate  130 . In this arrangement, a welding state of the non-coating portion  124  can be externally and easily checked (e.g., external checking of welding quality is facilitated) and welding reliability is improved. In addition, because the welding is performed in a state in which the non-coating portion  124  is exposed to the outside, and, in particular, butt welding is used as the welding method, welding efficiency may further be increased. Further, because the welding is performed at the end surface  124   b  of the non-coating portion  124  coupled to the collector plate  130 , it is possible to reduce the likelihood of or prevent welding beams from reaching the electrode assembly  120 , thereby improving product reliability. 
     The collector plate  130  is coupled to an end  124   b  of the non-coating portion  124 . The collector plate  130  is coupled to at least one of portions of the non-coating portions  124  connected to the positive electrode plate  121  and the negative electrode plate  122  by welding. In the following description, a coupling process of the collector plate  130  with the non-coating portion  124 , specifically, with one of the portions of the non-coating portion  124  connected to the positive electrode plate  121 , will be described by way of example. 
     The collector plate  130  is coupled to a portion of the non-coating portion  124  connected to the positive electrode plate  121  in pair. The collector plate  130  includes a first collector plate  131  and a second collector plate  132  coupled to the non-coating portion  124  in pair. 
     As shown in the embodiment of  FIG. 2 , the first collector plate  131  includes a first plate  131   a , and first protrusions  131   b  extending from the first plate  131   a  in a first direction (e.g., in a vertical direction). 
     The first plate  131   a  is positioned substantially perpendicular to the side surface  124   a  of the non-coating portion  124 , and the first protrusions  131   b  protrude in the non-coating portion  124  along the first direction. Here, each of the first protrusions  131   b  is formed to have a step height  131   c  from the first plate  131   a . Thus, the first protrusions  131   b  are positioned within the non-coating portion  124 , and places the non-coating portion  124  in the grooves  131   d  formed at both sides of the first protrusions  131   b  in a partitioned manner. In addition, the first protrusions  131   b  of the first collector plate  131  securely fix the non-coating portion  124  in mesh with the second collector plate  132 , and in such a state, the first protrusions  131   b  are coupled to the non-coating portion  124  by welding. Here, since the non-coating portion  124  (e.g., the end  124   b  of the non-coating portion) is positioned within the grooves  131   d  along the first protrusions  131   b , the welding is performed at edge portions of the first protrusions  131   b.    
     The second collector plate  132  is coupled to the first collector plate  131  in mesh therewith while the non-coating portion  124  is placed between the first collector plate  131  and the second collector plate  132 , which are coupled to each other. The second collector plate  132  includes a second plate  132   a , and a second protrusion  132   b  extending from the second plate  132   a  along the first direction. The second plate  132   a  is positioned substantially perpendicular to the side surface  124   a  of the non-coating portion  124  so as to correspond to (e.g., along the same plane as) the first plate  131   a  of the first collector plate  131 . The second protrusion  132   b  is formed to have a step height  132   c  from the second plate  132   a . Thus, the second protrusion  132   b  is placed within the non-coating portion  124 , and places the non-coating portion  124  into the grooves  132   d  formed at its both sides in a partitioned manner. Here, the second protrusion  132   b  has a shape corresponding to that of the first protrusion  131   b , and is meshed with and coupled to the first protrusion  131   b  of the first collector plate  131 . Thus, the non-coating portion  124  is positioned at a region where the first protrusion  131   b  of the first collector plate  131  and the second protrusion  132   b  of the second collector plate  132  are meshed with each other, followed by welding. As such, welding efficiency and reliability may be improved during welding of the non-coating portion  124 . 
     The current collecting terminal  140  is connected to the collector plate  130 . Specifically, the current collecting terminal  140  is connected to the first plate  131   a  of the first collector plate  131  by welding. The current collecting terminal  140  is attached to or welded to a surface of the first plate  131   a  of the collector plate  130  facing oppositely away from the surface of the collector plate  130  that is coupled to or contacting the non-coating portion  124 . 
     The current collecting terminal  140  includes a first plate  141  coupled to the collector plate  130  in the first direction, a second plate  142  extending from the first plate  141  in a second direction perpendicular to the first direction, and an electrode terminal  143  upwardly protruding from the second plate  142  in the first direction. The electrode terminal  143  upwardly protrudes through the cap plate  160  to then be connected to a charge/discharge circuit. In addition, a male thread may be provided on the outer circumference of the electrode terminal  143  to be engaged with the nut  180  in a subsequent process. 
     The first dielectric  150  is located at an upper side of the current collecting terminal  140 . The first dielectric  150  is placed between the second plate  142  of the current collecting terminal  140  and the cap plate  160 . The first dielectric  150  electrically separates (e.g., insulates) the current collecting terminal  140  from the cap plate  160 . In addition, the first dielectric  150  includes a terminal hole  151  formed therein, so that the electrode terminal  143  of the current collecting terminal  140  may extend through the terminal hole  151  to protrude upwardly toward the cap plate  160 . 
     The cap plate  160  is located at the upper side of the case  110  to hermetically seal the case  110 . The cap plate  160  is coupled to the case  110  and protects against leakage of an electrolyte contained within the case  110 . The cap plate  160  includes a terminal hole  161  formed therein, so that the electrode terminal  143  may extend through the terminal hole  161  to protrude upwardly. 
     The cap plate  160  may include a vent  162  formed substantially at its center. When gas is generated inside the case  110  due to overcharge, the vent  162  is opened earlier than the other parts, thereby exhausting the gas. 
     The second dielectric  170  is formed between the cap plate  160  and the electrode terminal  143  of the current collecting terminal  140 . The second dielectric  170  electrically separates (e.g., insulates) the cap plate  160  from the electrode terminal  143  of the current collecting terminal  140 . In addition, because the second dielectric  170  is also located at an upper portion of the cap plate  160 , it may electrically separate (e.g., insulate) the cap plate  160  and the nut  180  from each other when the nut  180  is engaged with the cap plate  160 . 
     The nut  180  is located at an upper side of the second dielectric  170 . The nut  180  has a female thread provided therein to be coupled to the male thread of the electrode terminal  143  of the current collecting terminal  140 . The nut  180  securely fixes the electrode terminal  143  of the current collecting terminal  140 , thereby fixing positions of the current collecting terminal  140  and the electrode assembly  120 . 
     Hereinafter, a method in which a collector plate and a non-coating portion are coupled to each other in a secondary battery according to one embodiment of the present invention will now be described in more detail. 
       FIGS. 7 and 8  illustrate a procedure in which a collector plate and a non-coating portion are coupled to each other in a secondary battery according to one embodiment of the present invention. 
     Referring first to the embodiment illustrated in  FIG. 7 , in the secondary battery  100 , the non-coating portion  124  is partitioned by the first protrusions  131   b  of the first collector plate  131 . The first protrusions  131   b , each having a step height  131   c , are inserted into the non-coating portion  124 , and the non-coating portion  124  is partitioned along edge portions of the first protrusions  131   b . That is to say, the non-coating portion  124  (e.g., edges along the end  124   b  of the non-coating portion  124 ) is positioned inside the grooves  131   d  located at both sides of each of the first protrusions  131   b.    
     The non-coating portion  124  is also partitioned by the second protrusions  132   b  of the second collector plate  132 . Because each of the second protrusions  132   b  has a step height  132   c , the second protrusions  132   b  are inserted into the non-coating portion  124 . Thus, the non-coating portion  124  (e.g., edges along the end  124   b  of the non-coating portion  124 ) is partitioned along edge portions of the second protrusion  132   b  and is positioned in the grooves  132   d  formed at both sides of each of the second protrusion  132   b.    
     Referring to  FIG. 8 , the first collector plate  131  and the second collector plate  132  are moved along a first direction to then be coupled to each other. Here, because the first collector plate  131  and the second collector plate  132 , which have the first protrusions  131   b  and the second protrusions  132   b , respectively, are coupled to each other while the first protrusions  131   b  and the second protrusions  132   b  are meshed with the corresponding grooves  131   d  and  132   d , respectively, the non-coating portion  124  is positioned between the first collector plate  131  and the second collector plate  132  in mesh with each other via their respective protrusions  131   b  and  132   b.    
     In addition, butt welding may be performed in a state in which the non-coating portion  124  is placed between the first collector plate  131  and the second collector plate  132 , thereby forming a welding portion  133 . Because the welding is performed after the non-coating portion  124  is exposed to the outside, welding efficiency may be increased. Further, because the welding portion  133  is exposed to an end surface  124   b  of the non-coating portion  124 , welding quality can be easily checked from the outside and welding reliability may be increased. Moreover, because welding beams irradiated when welding is performed are incapable of being transmitted to the inside of the non-coating portion  124 , product reliability can be increased. 
     As described above, in the secondary battery  100  according to one embodiment of the present invention, the collector plate  130  is welded to an end portion  124   b  of the non-coating portion  124  of the electrode assembly  120  using butt welding in a state in which the non-coating portion  124  is securely fixed between the first protrusions  131   b  of the first collector plate  131  and the second protrusions  132   b  of the second collector plate  132  in mesh with each other, thereby increasing welding efficiency. In addition, the welding portion  133  can be easily checked from the outside, thereby increasing welding reliability. Further, because the non-coating portion  124  has a thickness corresponding to the step height  131   c  or  132   c  of the first collector plate  131  or the second collector plate  132 , the capacity of the electrode assembly  120  can be increased by reducing the thickness of the non-coating portion  124 . 
     Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims and equivalents thereof.