Lithium Secondary Battery For Improving Bondability of Tab to Polymer Film

Abstract

A lithium secondary battery includes an electrode assembly having at least one tab which projects from one side of the electrode assembly, an external finishing material surrounding and sealing the tab except a distal end portion thereof and the electrode assembly, and polymer films interposed between the external finishing material and the tab to improve adhesion therebetween. When the tab has a thickness no less than a predetermined thickness, the tab is formed to have a sectional shape which ensures that an inside angle defined by one of upper and lower surfaces of the tab and an adjacent side surface of the tab becomes an obtuse angle, and the polymer films are formed to have protuberances on the inner surfaces thereof, so as to improve bondability between the tab and the polymer films.

1 . A lithium secondary battery including an electrode assembly having at least one tab which projects from a side of the electrode assembly, an external finishing material surrounding and sealing the tab except for a distal end portion thereof and the electrode assembly, and polymer films interposed between the external finishing material and the tab to improve adhesion between them, wherein, when the tab has a thickness no less than a predetermined thickness, the tab is formed to have a sectional shape which ensures that an inside angle defined by one of upper and lower surfaces of the tab and an adjacent side surface of the tab becomes an obtuse angle, so as to improve bondability between the tab and the polymer films. 
   
   
       2 . The battery as set forth in  claim 1 , wherein the predetermined thickness is no less than approximately 200 μm. 
   
   
       3 . The battery as set forth in  claim 2 , wherein the sectional shape of the tab is bilaterally symmetrical about a vertical axis. 
   
   
       4 . The battery as set forth in  claim 2 , wherein the sectional shape of the tab is rotationally symmetrical about a center thereof. 
   
   
       5 . The battery as set forth in  claim 2 , wherein the sectional shape of the tab is upwardly and downwardly symmetrical about a horizontal axis. 
   
   
       6 . The battery as set forth in  claim 2 , wherein the sectional shape of the tab has side surfaces, each of which is rounded and connects the upper and lower surfaces of the tab with each other. 
   
   
       7 . A lithium secondary battery including an electrode assembly having at least one tab which projects from a side of the electrode assembly, an external finishing material surrounding and sealing the tab except for a distal end portion thereof and the electrode assembly, and a pair of polymer films interposed between the external finishing material and the tab to improve adhesion therebetween and covering upper and lower surfaces of the tab, wherein, when the tab has a thickness no less than a predetermined thickness, protuberances are formed on oppositely facing surfaces of the pair of polymer films so that a distance measured between the protuberances positioned adjacent to both ends of the tab is greater than a width of the tab, so as to improve bondability between the tab and the polymer films. 
   
   
       8 . The battery as set forth in  claim 7 , wherein the predetermined thickness is no less than approximately 200 μm.