Electrolyte with weakly coordinating solvents for high-performance FeS2 cathode

Abstract

As the “blood” of batteries, the electrolyte is generally expected to be designed reasonably to meet the demands of stable energy storage in high energy density batteries. This study introduces a rational design for localized high-concentration electrolytes (LHCEs) by incorporating the weakly coordinating diluent 1, 1, 2, 2-tetrafluoro-1-methoxyethane (TFM) to modulate the solvation of Li+ alongside the anion and solvent 1, 2-diethoxyethane (DEE). The resulting LiFSI-DEE/2TFM electrolyte (1 M LiFSI in DEE/TFM at a ratio of 1:2, volume) demonstrates a significant efficacy in suppressing the dissolution of lithium polysulfides (LiPSs) while maintaining a good ionic conductivity. Moreover, this electrolyte facilitates the formation of a stable cathode-electrolyte interphase (CEI) and promotes uniform plating/stripping of Li+ at the lithium anode. Consequently, based on this electrolyte, the Li/FeS2 cells exhibit an exceptional specific capacity and a good cycling stability from room temperature to −20°C. Notably, even at −20°C, over 80 % of the room-temperature specific capacity (692.7 mAh g−1@150th) is retained for the cell using LiFSI-DEE/2TFM, showing its robust performance in challenging environments. Furthermore, the Li/FeS2 cell also demonstrates an outstanding durability at high current density (≥ 2 C) under room temperature.