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The lithium metal anode is notoriously unstable and reactive to electrolytes, forming brittle solid‐electrolyte interphase (SEI) layers with uneven distribution, exacerbating Li dendrites that ultimately limit the battery life. Here, this work passivates Li metal with electrolyte‐swellable polymer nanolayers deposited monolithically by the initiated chemical vapor deposition (iCVD) to reinforce the native SEI layers and stabilize their interface. The 100 nm iCVD poly(dimethylaminomethyl styrene) (pDMAMS) layer is swelled by 264% under a carbonate electrolyte, establishing the electrolyte‐filled soft scaffold for Li‐ion transport. Notably, the solvogel accommodates homogeneous Li2O‐free and Li2CO3‐rich native SEI layers, providing a record‐high Li‐ion transference number of 0.95 and ionic conductivity of 6.54 mS cm−1. The developed pDMAMS‐Li anodes extend the cycle life by 550% in Li–Li symmetric cells and 600% in LiNi0.6Mn0.2Co0.2O2 full cells compared to pristine Li metal. The mechanistic details of the swollen‐soft‐scaffold strategy are elucidated by depth profile analysis of the pDMAMS homopolymer compared to pDMAMS/electrolyte‐phobic copolymers, providing new insights to manage the interface of liquid‐state electrolyte and solid‐state Li metal by using a novel class of bifunctional solvogel. [ABSTRACT FROM AUTHOR]