Unique Non-Chelating Multidentate Ligand Tuning Solvation Structure and Interfacial Chemistry for High-Voltage Lithium Metal Batteries

Electrolyte engineering is a key strategy for achieving high-energy lithium metal batteries. Among various solvents, fluorinated ether-based electrolytes have shown promising results. However, these solvents often have several limitations: weak solvating ability, electrochemical reduction instability, and potential environmental hazards. Herein, a novel cyanated hexacyclic ether electrolyte (CHEE) is reported. The terminal cyano group (& horbar;CN) of solvent facilitates efficient Li+ transport through its coordination ability, while the electron-withdrawing nature of & horbar;CN weakens the solvating ability of the ether oxygen atom. This modification leads to anion-dominated solvation structures, wherein the nitrogen atom serves as the primary coordination site in the coordinated solvent. This unique non-chelating, multidentate ligand enables a robust solid-electrolyte interphase (SEI) and excellent electrochemical performance of lithium metal batteries. CHEE enables a Li-Cu cell to achieve a high coulombic efficiency of 99.5%, while a Li-NMC811 cell demonstrates a capacity retention of 91% after 300 cycles. Notably, the Li-NMC811 cell maintains stable cycling for 200 cycles at an elevated temperature of 60 degrees C. Furthermore, CHEE enables the operation of a Li-NMC811 pouch cell with a low N/P, achieves a high capacity of 1.25 Ah. This study highlights the potential of cyanated ether in developing novel electrolyte systems for high-performance lithium metal batteries.