The intrinsic reactivity of lithium (Li) toward ambient air, combined with insufficient cycling stability in conventional electrolytes, hinders the practical adoption of Li metal anodes in rechargeable batteries. Here, a bilayer interphase for Li metal is introduced to address both its susceptibility to corrosion in ambient air and its deterioration during cycling in carbonate electrolytes. Initially, the Li metal anode is coated with a conformal bottom layer of polysiloxane bearing methacrylate, followed by further grafting with poly(vinyl ethylene carbonate) (PVEC) to enhance anti-corrosion capability and electrochemical stability. In contrast to single-layer applications of polysiloxane or PVEC, the bilayer design offers a highly uniform coating that effectively resists humid air and prevents dendritic Li growth. Consequently, it demonstrates stable plating/stripping behavior with only a marginal increase in overpotential over 200 cycles in carbonate electrolytes, even after exposure to ambient air with 46% relative humidity. The design concept paves the way for scalable production of high-voltage, long-cycling Li metal batteries.