Interfacial fluoride engineering enabled robust LiF-rich solid electrolyte interphase to reduce active lithium loss in rechargeable lithium battery

Active lithium loss, which is caused by parasitic reactions due to the instability of solid electrolyte interphase (SEI) on the anodes, results in fast capacity fade of batteries. Constructing robust SEI layer is an effective way to reduce active lithium loss. Herein, we propose a AgF-coated separator (AgF-CS) to facilitate robust LiF-rich SEI on the anode during initial cycle. Electrochemical analysis and microstructure investigations confirm the formation of the LiF-rich SEI on the anode induced by the fluoride-containing coating layer. The fluoride-containing interfacial layer not only effectively enhances the reversible capacity of the SiO anode even under lean electrolyte (14 μL mAh−1) condition, but also prolongs the cycling life of lithium metal batteries by reducing the consumption of electrolyte and active lithium. The initial Coulombic efficiency (ICE) of LiFePO4||SiO full cell is increased from 43.68 % to 84.18 % with pretreatment by AgF-CS. As a result, the reversible capacity of LiFePO4||SiO full cell is increased by ∼124 % in contrast with that of the unmodified one. The strategy proposed here, benefiting from the simple manufacture, provides a feasible way to alleviate active lithium loss and elevate energy density of rechargeable lithium batteries.