Solvation‐Regulated Fluorinated Gel Polymer Electrolyte for Fast Li + Transport and Interphase Stabilization in Lithium Metal Batteries

Abstract

The development of gel polymer electrolytes (GPEs) with high ionic conductivity and stable electrode/electrolyte interface is crucial for realizing high‐energy‐density lithium metal batteries. In this work, a composite GPE is designed by incorporating 2,2,2‐trifluoroethyl methacrylate (TFEMA) and amino‐functionalized silica (KH550‐SiO 2 ) to synergistically optimize Li + transport kinetics and interfacial stability. Through hydrogen‐bonding interactions, the ─NH 2 groups on KH550‐SiO 2 regulate the Li + solvation environment, shifting ion association from ion aggregates (AGGs) toward solvent‐separated ion pairs (SSIPs) and contact ion pairs (CIPs) and restricting TFSI − mobility, thereby creating a weaker and more dynamic solvation structure with a high Li + transference number of 0.76 and an ionic conductivity of 1.03 mS cm −1 . Concurrently, the preferential reductive decomposition of TFEMA and the interfacial reaction of KH550‐SiO 2 collaboratively induce the formation of a stable solid electrolyte interphase (SEI) rich in LiF and Li 3 N. Benefiting from these advantages, the Li||LiFePO 4 full cell achieves a high capacity retention of 85% after 2000 cycles at a high rate of 5 C. This study provides an effective strategy for simultaneously enhancing the bulk Li + transport and interfacial properties of GPEs through molecular structure design.