Tailoring the electrolyte/electrode interface with 18-crown-6 and fluoroethylene carbonate for controlled and uniform lithium deposition

Abstract

Lithium metal is considered the top choice for anode materials due to its exceptionally high energy density (3860 mAh g⁻¹). However, its practical use in lithium metal anodes (LMAs) is limited by significant dendrite growth and an unstable interface between the anode and electrolyte. Herein, 18-crown-6 and fluoroethylene carbonate (FEC) were introduced as combined additives to improve the stability of the electrode/electrolyte interface and enhance long-term cycling performance. The presence of FEC promotes the formation of a LiF-rich solid electrolyte interphase (SEI), which guides lithium deposition and accelerates the transport of Li⁺ ions. Additionally, 18-crown-6 can eliminate “hotspots” during the lithium deposition and dissolution processes, leading to superior electrochemical performance. By incorporating 1 wt% 18-crown-6 and 10 vol% FEC, Li‖Cu half-cells achieved an impressive average coulombic efficiency of 97%, while Li‖Li symmetric cells demonstrated excellent stability for over 800 hours. When paired with LiFePO₄, the Li‖LFP full cell retained approximately 98% of its capacity and maintained a high average coulombic efficiency of 99% after 100 cycles at 0.5C. This research underscores the vital role of 18-crown-6 and FEC in electrolytes, revealing a fresh strategy to reduce lithium dendrite formation in lithium-based energy storage systems.