NOVELTY - A tab (104) has nickel layer (104x) formed in front and/or back of metal component, and compound film layer (104b) of aminated phenol polymer, trivalent chrome compound, and phosphorus compound formed in front, back and side of clamping portion (107). The tab is used for lithium ion battery consisting of main component containing electrolyte filled between positive and negative electrodes. While connecting with negative electrode, the tab is clamped such that front end protrudes outside exterior component (105), and clamping portion is heat-sealed.    USE - Tab is used for lithium ion batteries (claimed) used as power supply for electric vehicles and energy storage.    ADVANTAGE - The tab exhibits stable sealing performance, and enables economical manufacture of lithium ion batteries having excellent safety. The tab is not corroded by electrolyte and hydrofluoric acid. Elution of nickel layer is prevented. Peeling off of tab and exterior component is prevented. Since the metallic component has high electrical conductivity, electrical resistance of tab and loss of electrical energy are suppressed. The acid-modified polyolefin has excellent mechanical strength, heat resistance, and chemical resistance.    DETAILED DESCRIPTION - A tab consists of a nickel layer formed in the front and/or back of a metal component, and a compound film layer of aminated phenol polymer, trivalent chrome compound, and phosphorus compound formed in front, back and side of a clamping portion. The tab is used for a lithium ion battery consisting of a main component containing electrolyte filled between a positive electrode and a negative electrode. The positive and negative electrodes consist of the respective active material and collector. The main component is sealed in an exterior component, and the peripheral portion is thermobonded. While connecting with the negative electrode, the tab is clamped such that the front end protrudes outside the exterior component, and the clamping portion is heat-sealed. The metallic component comprises copper.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the tab.    Tab (104)    Compound film layer (104b)    Nickel layer (104x)    Exterior component (105)    Clamping portion (107)