Solubilized LiNO3 by the cationic size effect of CsF for lithium metal anode protection and dendrite formation prevention in carbonate electrolyte

Abstract

Much research has been conducted on lithium metal anodes because of their high theoretical specific capacity and low redox potential. However, the iterative side reactions of lithium and poor solubility of LiNO₃ in routinely used ester-based electrolyte are major obstacles. Based on the ‘cation size effect’, CsF was introduced in this work to solubilize LiNO₃ with Cs⁺ ions, which possess the maximum metal ion radius. The formation of a dense LiF-rich solid electrolyte interface (SEI) prevents severe side reactions of the lithium metal anode in the carbonate electrolyte. Moreover, the similar potentials of Cs⁺ and Li⁺ prevent lithium dendrites from forming because of the self-healing electrostatic shield mechanism. The additives comprehensively increased the coulombic efficiency of Li||Cu batteries from <80% to 98%, which also alleviated the sudden capacity decay of lithium metal batteries (Li||Li, Li||SPAN, Li||LFP, and Li||NCM523) by preventing the formation of lithium dendrites. Electrochemical characterization (LSV, CA, Tafel curves, CV, and EIS), XPS, and MD simulations proved the formation of a stable inorganic SEI. In situ optical visualization microscopy and scanning electron microscopy showed that the additives are conducive to the dense deposition of lithium. This strategy can be used to solve the genuine problems associated with lithium metal anodes from multiple aspects.