Fluorine‐Containing Phase‐Separated Polymer Electrolytes Enabling High‐Energy Solid‐State Lithium Metal Batteries

Abstract Solid‐state lithium (Li) metal batteries (LMBs) have been developed as a promising replacement for conventional Li‐ion batteries due to their potential for higher energy. However, the current solid‐state electrolytes used in LMBs have limitations regarding mechanical and electrochemical properties and interfacial stability. Here, a fluorine (F)‐containing solid polymer electrolyte (SPE) having a bi‐continuous structure of F‐containing elastomers and plastic crystals is reported. The trifluoroethyl acrylate‐based SPE (T‐SPE) exhibits high ionic conductivity over 10 −3 S cm −1 , superior mechanical elasticity, and robust LiF‐rich interphases at both the Li metal anode and the LiNi 0.83 Mn 0.06 Co 0.11 O 2 cathode. Full cells with thin T‐SPEs and low negative/positive capacity ratios below 0.5 at the high‐operating voltage of 4.5 V demonstrate a high specific energy of 538 Wh kg anode+cathode+electrolyte −1 and maintain 393 Wh kg −1 at a high specific power of 804 W kg anode+cathode+electrolyte −1 . The F‐containing phase‐separated SPE system provides a powerful strategy for achieving high‐energy and ‐power solid‐state LMBs.