Anion‐Regulated Ionic Liquid–Polymer Electrolytes for High‐Performance and Safe Lithium Metal Batteries

The development of safe and high‐performance polymer electrolytes is critical for advancing lithium metal batteries (LMBs). Herein, we report a PVDF‐HFP‐based polymer electrolyte incorporating two ionic liquids with different anions FSI − and TFSI − ‐to investigate their impact on structure and electrochemical behavior. The TFSI − ‐based system (PPIL) exhibits smaller particle size, reduced crystallinity, and enhanced amorphous β‐phase content, enabling improved ion mobility and a lower activation energy (69.0 kJ mol −1 ). Solid‐state NMR and Raman analyses reveal weaker Li + coordination in PPIL, consistent with its higher ionic conductivity (1.22 × 10 −3 S cm −1 ). Interfacial characterizations show that PPIL promotes the formation of a stable, LiF/Li 3 N‐rich SEI. As a result, LMBs using PPIL achieve over 2000 h of stable cycling, superior rate performance, and excellent thermal and mechanical safety in pouch cells. This work highlights the importance of ionic liquid anion design in optimizing polymer electrolytes for next‐generation energy storage systems.