Fluorine-Substituted Lithium Chloride Solid Electrolytes for High-Voltage All-Solid-State Lithium-Ion Batteries

Abstract

Lithium ternary halides are promising solid electrolytes, owing to their high ionic conductivity and reasonably high oxidative and chemical stability. Recently, fluorine substitution in Li 3 MCl 6 has been suggested as a promising approach for further enhancing oxidation stability. Accordingly, this study outlines a material design strategy for F-substituted Li 3 MCl 6 through systematic theoretical analyses. Calculations reveal that the mixing limit of F in Li 3 MCl 6−x F x is in the range of 0.5−1.5, and the resulting Li 3 MCl 6−x F x phases can retain ionic conductivity above 1 mS/cm up to x = 1.0. The calculations also predict that the formation of Fcontaining passivating phases could increase the oxidation potential for Li 3 MCl 5 F to ∼6.3 V. The proposed material design strategy is validated through the synthesis of Li 3 YCl 5 F, which is confirmed to show both high ionic conductivity and enhanced oxidation stability. The design guidelines presented herein can accelerate the potential use of halide-based electrolyte chemistries in high-voltage all-solid-state batteries.

Fluorinated Superionic Oxychloride Solid Electrolytes for High-Voltage All-Solid-State Lithium Batteries

“…Theoretical calculations suggest that fluorides possess superior oxidation stability compared to other halides, oxides, and sulfides, with stability even exceeding 6 V vs Li + /Li, as fluorine has the strongest electronegativity, which renders it resistant to oxidation. , Meanwhile, in situ formed fluorine-containing or fluorinated cathode-electrolyte interfaces (CEIs) are generally regarded as beneficial to high-voltage cathode materials due to their electrochemical stability and ability to transport Li + ions. − Therefore, fluorinating SEs has been regarded as a promising solution to stability issues, with several exploratory efforts having been made on various SEs. − …”