In Situ Polymerized Polyfluorinated Crosslinked Polyether Electrolytes for High‐Voltage Lithium Metal Batteries

Abstract In situ polymerized polyether electrolytes are promising for solid‐state Li metal batteries due to their high ionic conductivity and excellent interfacial contact. However, their practical application is hindered by Li dendrite formation, interfacial degradation, and limited oxidative stability. Herein, we propose an in situ polymerized polyfluorinated crosslinked polyether electrolyte (PDOL‐OFHDBO), synthesized by copolymerizing 1,3‐dioxolane (DOL) with 2,2′‐(2,2,3,3,4,4,5,5‐octafluorohexane‐1,6‐diyl)bis(oxirane) (OFHDBO) as a polyfluorinated crosslinker. The electron‐withdrawing polyfluorinated groups endow PDOL‐OFHDBO with enhanced oxidative stability and interfacial compatibility, while reducing the solvation power of the polymer matrix to promote an anion‐derived inorganic‐rich solid electrolyte interphase for uniform Li deposition. Consequently, PDOL‐OFHDBO exhibits a wide electrochemical stability window (>5.6 V) and enables long‐term stable Li plating/stripping for over 1100 h. Furthermore, Li||LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) full cells utilizing PDOL‐OFHDBO demonstrate outstanding cycling stability with high‐loading cathodes (≈3.8 mAh cm⁻²) and thin Li anodes (50 µm), achieving capacity retention of 95.5% and 89.1% over 100 cycles at cut‐off voltages of 4.3 and 4.5 V, respectively. Remarkably, Ah‐level Li||NCM811 pouch cells deliver an impressive specific energy of 401.8 Wh kg⁻¹, highlighting their potential for practical solid‐state Li metal batteries.