Investigation of fluoroethylene carbonate-containing ether-ester hybrid electrolytes for anode-free lithium metal batteries

Abstract

In anode-free lithium-metal battery (AFLMB), the electrolyte interacts with lithium metal to form a solid electrolyte interphase (SEI) layer. This SEI layer plays a critical role in maintaining battery performance by influencing initial charge-discharge capacities and long-term cycling stability. Ether-ester hybrid electrolytes are one of the most potential electrolytes for tackling these challenges. In this study, fluoroethylene carbonate (FEC) solvent is incorporated into a conventional ether electrolyte (1 M lithium bis(fluorosulfonyl)imide salt (LiFSI) - 0.3 M lithium nitrate (LiNO₃) in dimethyl ether of ethylene glycol (DME): 1,3-dioxolane (DOL) = 5:5 (v:v)) to examine its effects on SEI formation and AFLMB performance in the so-called FEC-containing ether-ester hybrid electrolytes. The electrolytes with optimized FEC addition facilitated the salvation of LiFSI and formed more inorganic components in the SEI layer, resulting in a higher initial discharge-specific capacity of approximately 158.5 mAh g⁻¹ and a coulombic efficiency of about 89.5 %. However, with increased cycling, the SEI layer in FEC-containing electrolytes was prone to break, which gradually deteriorated the cycling performance. In contrast, the ether-based electrolyte, though less effective in initial charge-discharge phases, demonstrated long-term cycling stability with a coulombic efficiency of around 98 %.