Fluorine‐Cyano‐Containing Gel Polymer Electrolyte Toward High‐Energy‐Density Lithium Metal Batteries

Gel polymer electrolytes (GPEs) are crucial for advancing the development of safe, high‐energy‐density lithium batteries. However, conventional GPEs often suffer from limited oxidation stability at high voltages and poor interface compatibility with lithium anodes. Here, we report a fluorine‐cyano‐containing crosslinked gel polymer electrolyte (FNGPE), which consists of strong electron‐withdrawing fluorine and cyano groups. The fluorine groups induce an anion‐rich solvation structure and promote the formation of a robust, inorganic‐rich solid electrolyte interphase on the lithium metal anode, effectively suppressing dendrite growth and ensuring exceptional interfacial stability; the cyano groups facilitate efficient Li + transport through strong coordination, significantly improving ionic conductivity and Li + transference number while enhancing oxidation stability. Benefiting from the synergistic effects of these dual functional groups, the resulting FNGPE exhibits excellent compatibility with lithium metal anodes and high nickel transition metal oxide cathodes (NCM811). A wide electrochemical window to 5.1 V is obtained, with a high Li + transference number of 0.61. The Li||Li symmetric cells with FNGPE cycle stably for over 2000 h at 0.5 mA cm −2 , and the Li||NCM811 batteries retain 80% capacity after 460 cycles under a cut‐off voltage of 4.5 V. Our findings introduce a promising electrolyte design for high‐energy‐density lithium metal batteries.