Lithium (Li) metal batteries hold significant promise in elevating energy density, yet their performance at ultra-low temperatures remains constrained by sluggish charge transport kinetics and the formation of unstable interphase. In conventional electrolyte systems, lithium ions are tightly locked in the solvation structure, thereby engendering difficulty in the de-solvation process and further exacerbating solvent decomposition. Herein, we propose a new push-pull electrolyte design strategy, utilizing molecular electrostatic potential (ESP) screening to identify 2,2-difluoroethyl trifluoromethanesulfonate (DTF) as an optimal co-solvent. Importantly, DTF exhibits a moderate ESP minimum (-21.0 kcal mol^-1) to strike a balance between overly strong and overly weak Li ionaffinity, which allows the sulfonyl group to effectively pull Li ions without disrupting the anion-rich solvation structure. Simultaneously, the difluoromethyl group, with a high ESP maximum (37.3 kcal mol^-1), pushes away solvent molecules via competitive hydrogen bonding. This design reconstructs existing solvation structures and expedites Liion de-solvation. Furthermore, fluorinated DTF demonstrates excellent stability at elevated voltage and facilitates the formation of robust inorganic-rich interphases. Impressively, rapid charge transfer kinetics can be achieved employing designed electrolyte and the LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) ||Li cells demonstrate excellent charge-discharge cycling stability with a high capacity exceeding 153 mAh g^-1 even at -40 ^oC, retaining over 93% of initial capacity after 100 cycles under a 4.8 V charging cut-off. This work provides insights into the design of low-temperature electrolytes with wide electrochemical window, advancing the development of batteries for extreme conditions.

Link: https://pubs.acs.org/doi/full/10.1021/jacs.4c09027