Synergistic Effects of LiNO₃ and LiN(SO₂CF₃)₂ on Reversibility of Li Deposition/Dissolution in Sulfolane-Based Electrolytes

Lithium metal is a promising anode material for next-generation rechargeable batteries. However, significant challenges remain, including the growth of Li dendrites and electrolyte decomposition on the Li electrode. LiNO 3 has been widely studied as an electrolyte additive because of its ability to form a Li 3 N-rich solid-electrolyte interphase (SEI) on Li, thereby suppressing electrolyte decomposition. In this study, sulfolane (SL) was employed as a solvent having high LiNO 3 solubility, and the electrochemical properties of LiNO 3 /SL electrolytes were investigated systematically. The LiNO 3 /SL electrolytes facilitated the formation of an SEI derived from LiNO 3 and enabled the uniform deposition of Li. However, the ionic conductivity of LiNO 3 /SL electrolyte was low due to the low degree of dissociation of LiNO 3 . The ionic conductivity was improved by mixing a highly dissociative LiN(SO 2 CF 3 ) 2 (LiTFSA) with LiNO 3 in SL, and the coulombic efficiency for Li deposition/dissolution was improved simultaneously. Further, the electrode potential of Li in the SL-based electrolyte became more positive with the incorporation of LiTFSA, weakening the reducing power of Li. Consequently, the LiNO 3 -derived SEI and the weak reducing power of Li synergistically suppressed the reductive decomposition of SL-based electrolyte and enhanced the reversibility of Li deposition/dissolution.