The metallic lithium(Li)is the ultimate option in the development of anodes for high-energy secondary batteries.Unfortunately,inferior cycling reversibility and Li dendrites growth of Li metal as anode enor-mously impede its commercialization.Here,a uniform Lil protective layer is constructed on Li metal anode via a facile and direct solid-gas reaction of Li metal with iodine vapor.The pre-constructed Lil layer possesses more steadily and faster Li ion transport than the conventional SEI layer and contributes to a steady interface for the Li metal anode,which affords a smooth Li deposition morphology without Li den-drites formation.The symmetrical cell with the Li metal anode protected by Lil layer exhibits a longer cycling lifetime of over 700 h at a current density of 1 mA cm-2 with Li plating capacity of 1 mAh cm-2.Moreover,the Lil layer protected Li metal anode can still remain high capacity retention of 74.6％after 500 cycles in the full cell paired with NCM523 cathode.The work proposes an easy and effective method to fabricate a uniform and stable protective layer on the Li metal anode and offers a practicable thinking for the commercial implementation of Li metal batteries.