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All-Fluorinated Electrolyte, Cathode Electrolyte Interphase, Quasi-Solid-Phase Conversion, Sodium–Sulfur Batteries, Solvation Structure, Cathodes, Polysulfides, Secondary batteries, Sodium, Sodium compounds, Solvation, Sulfur, All-fluorinated electrolyte, Cathode electrolyte interphase, Cyclability, Na/S batteries, Phase conversion, Quasi-solid-phase conversion, Sodium-sulfur batteries, Solid phasis, Solid-phase, Solvation structure, Electrolytes
Abstract:
Rechargeable room-temperature sodium–sulfur (RT Na–S) batteries are a promising energy storage technology, owing to the merits of high energy density and low cost. However, their electrochemical performance has been severely hindered by the poor compatibility between the existing electrolytes and the electrodes. Here, we demonstrate that an all-fluorinated electrolyte, containing 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA) solvent, 1,1,2,2-tetrafluoroethyl methyl ether (MTFE) anti-solvent and fluoroethylene carbonate (FEC) additive, can greatly enhance the reversibility and cyclability of RT Na–S batteries. A NaF- and Na3N-rich cathode electrolyte interphase derived from FDMA and FEC enables a “quasi-solid-phase” Na–S conversion, eliminating the shuttle of polysulfides. The MTFE not only reduces polysulfide dissolution, but also further stabilizes the Na anode via a tailored solvation structure. The as-developed RT Na–S batteries deliver a high capacity, long lifespan, and enhanced safety. © 2022 Wiley-VCH GmbH.
