Lithium metal as an ideal anode for next-generation batteries has attracted extensive attention. However, rough electrodeposition, severe parasitic reactions and uncontrolled lithium dendrites cause fast battery fading. Engineering a dendrite-free lithium metal anode for long cycling life is critical for its future development. Here, we reported a conformal, aluminum-based polymer coating with highly crosslinking structure on lithium using molecular layer deposition (MLD) to control undesirable reactions. This hybrid organic/inorganic film functions as an artificial interface to stabilize lithium stripping/deposition and enables minimal side reactions and dendrite-free lithium anodes. Alucone coated Li leaded to several times longer cycle life in a large current rate and achieved steady Coulombic efficiency of 99% at 0.4 mA/cm². The protected Li also accomplished much improved performance of lithium-sulfur (Li-S) batteries with a high mass-loading of ~5 mg/cm². Our proposal and findings offer an efficient avenue towards a highly stable lithium anode and the application in high energy density Li-S batteries.