Non-Fluorinated Cyclic Ether-Based Electrolyte with Quasi-Conjugate Effect for High-Performance Lithium Metal Batteries

Fluorinated ether-based electrolytes are commonly employed in lithium metal batteries (LMBs) to attenuate the coordination ability of ether solvents with Li+ and induce inorganic-rich interphase, whereas fluorination inevitably introduces exorbitant production expenses and environmental anxieties. Herein, a non-fluorinated molecular design strategy has been conceptualized by incorporating methoxy as an electron-donating group to generate a quasi-conjugate effect for tuning the affinity of Li+-solvent, thereby enabling the cyclic ether solvent 2-methoxy-1,3-dioxolane with weak solvation ability and exceptional Li metal-compatibility. Accordingly, the optimized electrolyte exhibits anion-dominant solvation structure for inorganic-rich interphase and fulfills an impressive Li plating/stripping Coulombic efficiency of 99.6%. As-fabricated Li||LiFePO4 full cells with limited Li (N/P = 2.5) showcase a high capacity retention of 83% after 150 cycles, indicating excellent cycling stability. Moreover, the full LMBs demonstrate exceptional tolerance towards a wide temperature range from -20 oC to 60 oC, displaying a remarkable capacity retention of 90% after 110 cycles at -20 oC. Such a molecular design strategy offers a promising avenue for electrolyte engineering beyond fluorination in order to cultivate high-performance LMBs.