Constructing a uniform lithium iodide layer for stabilizing lithium metal anode

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 enormously impede its commercialization. Here, a uniform LiI 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 LiI 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 dendrites formation. The symmetrical cell with the Li metal anode protected by LiI 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 LiI 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.