The effects of lithium salt and solvent on lithium metal anode performance

In this study, the effects of lithium salts (i.e. LiPF 6 , LiClO 4 and LiN(SO 2 CF 3 ) 2 ) and solvents (i.e. carbonate and ether type) on the Li metal anode electrochemical performance are systematically studied. It is found that LiN(SO 2 CF 3 ) 2 , denoted as LiTFSI, in 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) as electrolyte offers the best performance with a cycle life of 1100 h under the capacity of 2 mAh/cm 2 and current density of 2 mA/cm 2 . Lithium stripping/plating produces porous loose lithium powders rather than dendrites. Both lithium salts and solvents have influences on the lithium powder nucleation and growth. In the LiTFSI-DOL/DME system, lithium metal after stripping/plating has a relative flat and dense surface, which concomitantly brings in a low charge transfer resistance , low solid electrolyte interphase resistance, and elongated cycle life. A high Li + transference number and a high Li + -solvent interaction force are beneficial to an even Li + flux and a stable Li-electrolyte interface. This study sheds light on the importance of electrolytes for high performance lithium metal anodes.