In situ Polymerized Solid‐State Electrolyte Enabling Inorganic‐Organic Dual‐Layered SEI Film for Stable Lithium Metal Batteries

Abstract In situ polymerization of cyclic ethers is a promising strategy to construct solid‐state lithium (Li) metal batteries with high energy density and safety. However, their practical applications are plagued by the unsatisfactory electrochemical properties of polymer electrolytes and the unstable solid electrolyte interphase (SEI). Herein, organic perfluorodecanoic acid (PFDA) is proposed as a new initiator to polymerize 1,3‐dioxolane electrolyte (PDOL), which enables the as‐obtained PDOL electrolyte to deliver greatly enhanced ionic conductivity and broadened electrochemical window. Besides, the experimental data and theoretical calculations demonstrate a dual‐layered SEI with PFDA‐derived organic component on the top and LiF at the bottom constructed on the surface of Li metal, which can provide enough mechanical strength to suppress Li dendrite growth and high flexibility to accommodate volume fluctuations during the repeated cycling. As a result, the Li symmetric cells with PFDA‐induced PDOL electrolyte (P‐PDOL) can achieve a superior plating/stripping cycle for 1400 h at 0.3 mA cm −2 . Additionally, the Li||P‐PDOL||LiFePO 4 (LFP) full cells maintain stable cycling over 300 times at 0.5 C. This work offers a potential strategy to simultaneously prepare high‐performance PDOL electrolytes and stabilize the Li metal/PDOL interface, providing new research insights to advance solid‐state Li metal batteries toward practical applications.