Abstract: Lithium metal is regarded as one of the most promising anode materials for next- generation high-energy-density batteries because of its ultrahigh theoretical specific capacity and low electrochemical potential. However, the practical application of high-voltage lithium metal batteries (LMBs) is still severely hindered by uncontrolled lithium dendrite growth, unstable solid electrolyte interphase (SEI), and the poor oxidative stability of conventional ether-based electrolytes. Herein, a localized high-concentration electrolyte (LHCE) is constructed by introducing the fluorinated co-solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE). Combined molecular dynamics simulations and in-situ optical microscopy reveal that the strong electronegativity of fluorine atoms in TTE effectively regulates the anion coordination structure, promotes the formation of an inorganic-rich SEI, markedly improves Li+ transport kinetics, and suppresses lithium dendrite growth. Electrochemical measurements show that the Li||Cu half-cell with LHCE delivers an average Coulombic efficiency of 98.5% after 670 cycles at 0.5 mA cm-2. The full cells based on LHCE also exhibit excellent electrochemical performance: the Li||LFP cell retains 97.4% of its capacity after 400 cycles at 1.0 C, while the Li||NCM811 cell maintains 68.8% capacity retention after 500 cycles at 1.0 C. This work provides an effective strategy for electrolyte design and interfacial regulation in high-voltage LMBs.

Key words: Lithium metal battery, Localized high-concentration electrolyte, TTE cosolvent; Interphase regulation, Electrochemical performance