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.

金属锂（​​Li）是开发高能二次电池阳极的最终选择。不幸的是，不良的循环可逆性和作为阳极的锂会阻碍锂金属的生长，极大地阻碍了其商业化。在这里，通过锂金属与碘蒸气的简便直接固-气反应，在锂金属阳极上构建了均匀的锂保护层。预构造的LiI层比常规SEI层具有更稳定和更快的Li离子传输，并为Li金属阳极提供了稳定的界面，从而提供了平滑的Li沉积形态而没有Li树枝状晶体的形成。具有由LiI层保护的Li金属阳极的对称电池在1 mA cm ^-2的电流密度下具有700 h以上的较长循环寿命Li镀覆容量为1mAh cm ^-2。此外，在与NCM523阴极配对的完整电池中经过500次循环后，受LiI层保护的Li金属阳极仍可保持74.6％的高容量保持率。这项工作提出了一种简单有效的方法，以在锂金属阳极上制造均匀稳定的保护层，并为锂金属电池的商业化实施提供了实用的思路。