Fluorinated Deep Eutectic Gel Electrolytes with Simultaneously Enhanced Mechanical Strength and Ionic Conductivity for Solid‐State Lithium Metal Batteries

Abstract

ABSTRACT Gel polymer electrolytes for lithium‐metal batteries face an inherent trade‐off between mechanical strength and ionic conductivity. Herein, we present a molecular‐level strategy that harnesses competitive hydrogen‐bonding interactions to spontaneously generate a nanoscale phase‐separated architecture in the deep eutectic gel (DEG) electrolyte. Through one‐step in‐situ copolymerization of acrylamide and N,N ‐dimethylacrylamide within a trifluoromethyl‐functionalized deep eutectic solvent comprising N ‐methyl‐2,2,2‐trifluoroacetamide (TNMA) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), an interpenetrating network is formed, in which rigid polyacrylamide‐rich domains reinforce the matrix while polydimethylacrylamide‐rich channels facilitate ion transport. Driven by the competition between polymer–polymer and polymer–solvent hydrogen bonds, the resulting DEG electrolyte achieves an exceptional ionic conductivity of 2.99 mS cm −1 at 30°C, an excellent Li + transference number of 0.78, and a remarkable tensile strength of 11.4 MPa with 473% elongation. Meanwhile, TNMA, together with TFSI − , regulates the Li + solvation structure and interfacial chemistry, promoting the formation of a LiF‐rich interphase through fluorinated‐solvent‐ and anion‐involved interfacial reactions. The resulting Li||Li symmetric cells operate for over 3500 hours (0.1 mA cm −2 ), and Li|DEG|NCM811 cells retain 77.5% capacity after 400 cycles at 2 C. This work establishes competitive molecular interactions as a design principle for next‐generation gel polymer electrolytes.