Voltage-Responsive Rapid Defluorination of Free Anions in the Inner Helmholtz Layer for High-Performance Lithium Metal Batteries

The intrinsically low oxidative stability of ether solvents, together with the formation of unstable solid electrolyte interphases in ether-based electrolytes, imposes significant limitations on their development in high-voltage lithium metal batteries. To address these issues, this work utilizes the voltage-responsive advantages of free anions and the susceptibility to cleavage of the S–F bond in FSI – anions, promoting the accumulation of FSI – within the inner Helmholtz layer and facilitating rapid defluorination. The designed ether-based electrolyte with a solvent-separated ion pair-dominated solvation structure leads to an increased LiF content in the electrode–electrolyte interphases and achieves a high average Coulombic efficiency of 99.2% for lithium plating/stripping. Furthermore, the Cu@Li||NCM811 full cell exhibits a capacity retention of 92.2% over 450 cycles at a cutoff voltage of 4.3 V. This work provides new insights into the electrical double layer and electrode interphase design, expanding the application of ether-based electrolytes in high-voltage LMBs.