The urgent need for high energy batteries is pushing the battery studies toward the Li metal and solid‐state direction, and the most central question is finding proper solid‐state electrolyte (SSE). So far, the recently studied electrolytes have obvious advantages and fatal weaknesses, resulting in indecisive plans for industrial production. In this work, a thin and dense lithiated polyphenylene sulfide‐based solid state separator (PPS‐SSS) prepared by a solvent‐free process in pilot stage is proposed. Moreover, the PPS surface is functionalized to immobilize the anions, increasing the Li+ transference number to 0.8−0.9, and widening the electrochemical potential window (EPW > 5.1 V). At 25 °C, the PPS‐SSS exhibits high intrinsic Li+ diffusion coefficient and ionic conductivity (>10−4 S cm−1), and Li+ transport rectifying effect, resulting in homogenous Li‐plating on Cu at 2 mA cm−2 density. Based on the limited Li‐plated Cu anode or anode‐free Cu, high loadings cathode and high voltage, the Li‐metal batteries (LMBs) with polyethylene (PE) protected PPS‐SSSs deliver high energy and power densities (>1000 Wh L−1 and 900 W L−1) with >200 cycling life and high safety, exceeding those of state‐of‐the‐art Li‐ion batteries. The results promote the Li metal battery toward practicality. A high‐crystallized, thin, and dense lithiated polyphenylene sulfide (PPS) based solid state separator is prepared by a solvent‐free process with repeated rolling, which is functionized by anions binding and protected by polyethylene (PE) on the anodic side, achieving high voltage and homogenous Li plating.