Fluorinated Segmental Dilution Constructs Low‐Temperature Tolerant Localized High‐Concentration Polymer Electrolytes for Lithium Metal Batteries

ABSTRACT Lithium metal batteries (LMBs) encounter critical challenges at low temperatures due to the sluggish ion transport and unstable lithium deposition. Localized high concentration electrolytes, a representative weak−solvation strategy, have been extended to gel polymer electrolytes with tunable solvation structures and improved low−temperature performance. Herein, a moderately fluorinated segment is selected for the localized high concentration polymer electrolytes (LHCPE) by balancing dilution, salt dissociation, and copolymerization compatibility through side chain screening. Fine−tuning the dilution effect within the polymer matrix enables the formation of anion−rich coordination that maintains structural integrity at low temperatures, reducing reliance on polymer segmental motion and enhancing Li + transport with high ionic conductivities (2.12 × 10 −3 S·cm −1 at 25°C). The compact, anion‐dominated solvation structure promotes the formation of an inorganic−rich solid electrolyte interphase, supporting long−term symmetric cell operation for over 4000 h at room temperature and 2800 h at −20°C. The initial capacity of the Li||NCM811 full cells retained 74.72% and 51.68% of their room‐temperature capacity at −20°C and −40°C, respectively, achieved 92.62% capacity retention after 125 cycles at −20°C and 80.91% after 55 cycles at −40°C. This study provides insight for the rational design of LHCPEs toward high−performance LMBs in extreme environments.