Lithium metal batteries promise higher energy densities than current lithium-ion batteries but require novel electrolytes to extend their cycle life. To promote electrolyte stability against lithium metal and improve the reversibility of lithium deposition/stripping, several electrolyte design strategies have been pursued. For example, high concentration electrolytes (HCEs) and localized high concentration electrolytes (LHCEs) produce solvation structure rich in salt aggregates and ion pairs, which can increase lithium metal cycling Coulombic efficiency to as high as 99.5%. Recently, molecular design of fluorinated ether solvents also leads to high lithium metal Coulombic efficiency of up to 99.9% in single-solvent-single-salt ~ 1 M electrolytes. In addition, fluorinated acetals, fluorinated carbonates, and fluorinated sulfonamides are also reported to enable efficient lithium metal cycling. Among those novel electrolytes, fluorinated solvents or diluents are frequently used because fluorinated moieties are known to yield LiF as a preferable component in solid electrolyte interphase (SEI). However, fluorinated groups are believed to weaken ion solvation as most fluorinated solvents show poorer solvation ability or lower ionic conductivity compared to their nonfluorinated counterparts. The trade-off between SEI passivation and ion solvation limits further optimization of fluorinated electrolytes.In this work, we synthesize tris(2-fluoroethyl) borate (TFEB) as a new fluorinated borate ester solvent. Interestingly, moderately fluorinated TFEB shows unexpectedly high lithium salt solubility (~1 M LiFSA) while the nonfluorinated triethyl borate (TEB) and heavily fluorinated tris(2,2,2-trifluoroethyl) borate (TTFEB) can hardly dissolve lithium salt. Through density functional theory (DFT) calculations and ab-initio molecular dynamics (AIMD) simulations, we show that the partially fluorinated -CH2F group in TFEB acts as primary coordination site that promotes lithium salt dissolution. The electrochemical property of TFEB electrolyte is then compared to the methoxy polyethyleneglycol borate esters reported in literature. Owing to the fluorinated solvent structure, TFEB electrolyte passivates lithium metal with LiF-rich SEI and supports compact lithium deposition morphology, high lithium metal Coulombic efficiency, and stable cycling of lithium metal/LiFePO4 cells. This work ushers in a new electrolyte design paradigm where partially fluorinated moieties enable salt dissolution and can serve as primary ion coordination sites for next-generation electrolytes. Figure 1