Ultrathin lithium metal anodes for high-efficiency lithium batteries: synergizing surface LiF and Lithiophilic alloying

Lithium metal batteries are considered one of the most promising candidates for next-generation energy storage systems. However, challenges such as dendrite formation, unstable cycling, and low lithium utilization have severely hindered their practical implementation. Herein, we propose a universal and scalable strategy for fabricating ultrathin lithium anodes by integrating lithiophilic alloys and metal fluoride coatings onto current collectors through a simple SnF₂-based gas-phase reaction. A roll-to-roll system enables scalable production on various metal substrates, as demonstrated by Ni mesh coated with Ni₃Sn₂ and NiF₂. Electrochemical lithium deposition and molten infusion induce in situ Li-Sn alloy formation and LiF surface migration, which synergistically enable uniform plating, interface stabilization, and high lithium utilization. The resulting anodes deliver tunable areal capacities of 3–10 mAh cm⁻², effectively overcoming the fabrication limitations of lithium foils thinner than 50 μm and significantly reducing lithium consumption. Specifically, ultrathin lithium anodes with a capacity of 3.4 mAh cm⁻² exhibit stable cycling over 2200 h in symmetric cells. Full cells with LiFePO₄ cathodes deliver an average Coulombic efficiency of 99.8 % over 200 cycles at 0.5 C.