Understanding the role of additive in the solvation structure and interfacial reactions on lithium metal anode

Abstract

It is instructive to explain the mechanism of action of additives as much as possible for the development of electrolytes. Recently, lithium disfluorobis(oxalato)phosphate (LiDFBOP) has been reported to show significant improvements in the solid electrolyte interphase (SEI) and battery performance in Li–S battery. In this work, the action mechanism of LiDFBOP in ether electrolyte was investigated in detail by a first-principles study. It was found that LiDFBOP preferentially decomposes on the anode, and the local environment after decomposition has a significant influence on the subsequent reaction. In addition, the participation of DFBOP⁻ significantly affected the solvated structure and the trend in molecular decomposition. The addition of appropriate LiDFBOP weakened the strong binding between Li ion and the FSI⁻ anion, and increased the content of 1,3-dioxolane in the solvated structure, thus improving the formation of the organic SEI. On the other hand, the LUMO redistribution induced by LiDFBOP is beneficial for protection of solvents. The possible characteristics of the new additive and the importance of dosage are also summarized in terms of the mechanism of action.