Abstract： 

Li metal has been widely regarded as a promising anode for  next‐generation batteries due to its high theoretical capacity and low  electrochemical potential. The unstable solid‐electrolyte interphase  (SEI) and uncontrollable dendrite growth, however, incur severe safety  hazards and hamper the practical application of Li metal anodes. Herein,  an advanced artificial SEI layer constructed by [LiNBH]_n chains, which are crosslinked and self‐reinforced by their intermolecular Li-N  ionic bonds, is designed to comprehensively stabilize Li metal anodes  on a molecular level. Benefiting from its polymer‐like structure, the  [LiNBH]_n layer is flexible and effectively tolerates  the volume change of Li metal anodes. In addition, this layer with high  polarity in its structure, helps to regulate the homogeneous  distribution of the Li⁺ flux on Li electrodes via the further formation of Li-N bonds. The designed [LiNBH]_n layer is electrically nonconductive but highly ionically conductive, thus facilitating Li⁺ diffusion and confining Li deposition beneath the layer. Therefore, under the protection of the [LiNBH]_n layer, the Li metal anodes exhibit stable cycling at a 3 mA cm⁻²  for more than 700 h, and the full cells with high lithium iron  phosphate and sulfur cathodes mass loading also present excellent  cycling stability.