Competitive Solvation Enhanced Stability of Lithium Metal Anode in Dual-Salt Electrolyte.

Abstract

The development of lithium metal batteries is hindered by the low Coulombic efficiency and poor cycling stability of the metallic lithium. The introduction of consumptive LiNO₃ as an additive can improve the cycling stability, but its low solubility in the carbonate electrolytes makes this strategy impractical for long-term cycling. Herein we propose LiNO₃ as a cosalt in the LiPF₆-LiNO₃ dual-salt electrolyte to enhance the cycling stability of lithium plating/stripping. Competitions among the components and the resultant substitution of NO₃^- for PF₆^- in the solvation shell facilitate the formation of a Li₃N-rich solid electrolyte interphase (SEI) film and suppress the LiPF₆ decomposition. The highly Li⁺ conductive and stable SEI film effectively tailors the lithium nucleation, suppresses the formation of lithium dendrites, and improves the cycling performance. The competitive solvation has profound importance for the design of a complex electrolyte to meet the multiple requirements of secondary lithium batteries.