Effects of Fluorinated Diluents in Localized High‐Concentration Electrolytes for Lithium–Oxygen Batteries

Abstract

A stable electrolyte is critical for practical application of lithium–oxygen batteries (LOBs). Although the ionic conductivity and electrochemical stability of the electrolytes have been extensively investigated before, their oxygen solubility, viscosity, volatility, and the stability against singlet oxygen (1O2) still need to be comprehensively investigated to provide a full picture of the electrolytes, especially for an open system such as LOBs. Herein, a systematic investigation is reported on the localized high‐concentration electrolytes (LHCEs) using different fluorinated diluents in comparison with those of conventional electrolytes. The physical properties and activation energies for reactions with singlet oxygen (1O2) of these electrolytes are calculated by density functional theory. The electrochemical performances of LOBs using these electrolytes are compared. This study reveals that the correlation between the stability of the electrolytes and their physical and electrochemical properties depends strongly on the diluents in LHCEs. Therefore, it shines light on the rational design of new electrolytes for LOBs.

Current status and future perspectives of lithium metal batteries

“…Highly-concentrated electrolytes have shown benefits for both electrodes. Examples include 3 M LiTFSI/DME [406], 4 M LiNO 3 /DMSO [407] and more recently localized high-concentration electrolytes [408], which employ fluorinated diluents to improve viscosity, cost, O 2 solubility, and stability against 1 O 2 . They all have been shown to cycle lithium metal well under O 2 atmosphere.…”

Non‐Flammable Liquid and Quasi‐Solid Electrolytes toward Highly‐Safe Alkali Metal‐Based Batteries

“…After the TTE addition, the electrochemical performances of Li||LiNi 0.6 Mn 0.2 Co 0.2 O 4 (NMC622) cells were significantly improved, even if the cell was cycled up to 4.6 V ( Figure 2f). In addition, LHCEs are also beneficial for improving the performances of LiO 2 [40] and Li-S batteries. [41]…”

Investigating lithium metal anodes with nonaqueous electrolytes for safe and high-performance batteries

“…76,77 In recent years, localized high concentration electrolytes applying diluent to dilute high concentration electrolytes have attracted intense research interest. [78][79][80][81] In this system, the diluent is inert enough to dissolve the salts but miscible with the solvent; therefore the solvation structure of the high concentration electrolyte is preserved well, while the salt concentration and viscosity are lowered to a practical level. For example, Ren et al introduced a non-solvating uorinated ether of 1,1,2,2-tetrauoroethyl-2,2,3,3-tetrauoropropyl ether (TTE) to dilute highly viscous tetramethylene sulfone.…”