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

Li, Yuelin; Qin, Zuosu; Gao, Yuanhang; Zhang, Tao; Jiang, Yuhang; Yuan, Xiaoming; Zhang, Ning; Liu, Xiaohe et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

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<sup>-</sup> anions, promoting the accumulation of FSI<sup>-</sup> 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.