Unveiling the Role of Fluorination in Hexacyclic Coordinated Ether Electrolytes for High-Voltage Lithium Metal Batteries

作者：Lan‐Qing Wu, Zhe Li, Zhenyu Fan, Kun Li, Jia Li, Dubin Huang, Aijun Li, Yang Yang, Weiwei Xie, Qing Xiang Zhao · 发表于：Journal of the American Chemical Society · 年份：2024 · DOI：10.1021/jacs.3c11798 · 被引用次数：121 · 研究领域：Advanced Battery Materials and Technologies、Advancements in Battery Materials、Advanced Battery Technologies Research

Fluorinated ethers have become promising electrolyte solvent candidates for lithium metal batteries (LMBs) because they are endowed with high oxidative stability and high Coulombic efficiencies of lithium metal stripping/plating. Up to now, most reported fluorinated ether electrolytes are −CF 3 -based, and the influence of ion solvation in modifying degree of fluorination has not been well-elucidated. In this work, we synthesize a hexacyclic coordinated ether (1-methoxy-3-ethoxypropane, EMP) and its fluorinated ether counterparts with −CH 2 F (F1EMP), −CHF 2 (F2EMP), or −CF 3 (F3EMP) as terminal group. With lithium bis(fluorosulfonyl)imide as single salt, the solvation structure, Li-ion transport behavior, lithium deposition kinetics, and high-voltage stability of the electrolytes were systematically studied. Theoretical calculations and spectra reveal the gradually reduced solvating power from nonfluorinated EMP to fully fluorinated F3EMP, which leads to decreased ionic conductivity. In contrast, the weakly solvating fluorinated ethers possess higher Li + transference number and exchange current density. Overall, partially fluorinated −CHF 2 is demonstrated as the desired group. Further full cell testing using high-voltage (4.4 V) and high-loading (3.885 mAh cm –2 ) LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode demonstrates that F2EMP electrolyte enables 80% capacity retention after 168 cycles under limited Li (50 μm) and lean electrolyte (5 mL Ah −1 ) conditions and 129 cycles under e...