Push–Pull Electrolyte\nDesign Strategy Enables\nHigh-Voltage Low-Temperature Lithium Metal Batteries

Lithium (Li) metal batteries hold significant promise\nin elevating\nenergy density, yet their performance at ultralow temperatures remains\nconstrained by sluggish charge transport kinetics and the formation\nof unstable interphases. In conventional electrolyte systems, lithium\nions are tightly locked in the solvation structure, thereby engendering\ndifficulty in the desolvation process and further exacerbating solvent\ndecomposition. Herein, we propose a new push–pull electrolyte\ndesign strategy, utilizing molecular electrostatic potential (ESP)\nscreening to identify 2,2-difluoroethyl trifluoromethanesulfonate\n(DTF) as an optimal cosolvent. Importantly, DTF exhibits a moderate\nESP minimum (−21.0 kcal mol<sup>–1</sup>) to strike\na balance between overly strong and overly weak Li ion affinity, which\nallows the sulfonyl group to effectively pull Li ions without disrupting\nthe anion-rich solvation structure. Simultaneously, the difluoromethyl\ngroup, with a high ESP maximum (37.3 kcal mol<sup>–1</sup>),\npushes solvent molecules via competitive hydrogen bonding. This design\nreconstructs existing solvation structures and expedites Li ion desolvation.\nFurthermore, fluorinated DTF demonstrates excellent stability at elevated\nvoltage and facilitates the formation of robust inorganic-rich interphases.\nImpressively, rapid charge transfer kinetics can be achieved employing\ndesigned electrolyte, and the LiNi<sub>0.8</sub>Mn<sub>0.1</sub>Co<sub>0.1</sub>O<sub>2</sub> (NMC811)||Li cells demonstrate excellent charge–discharge\ncycling stability with a high capacity exceeding 153 mAh g<sup>–1</sup> even at −40 °C, retaining over 93% of initial capacity\nafter 100 cycles under a 4.8 V charging cutoff. This work provides\ninsights into the design of low-temperature electrolytes with a wide\nelectrochemical window, advancing the development of batteries for\nextreme conditions.