Ultrathin LiF-rich solid electrolyte interphase for stable long-life cycling stabilization of lithium metal anodes

Lithium-metal anodes have attracted widespread attention owing to their high specific capacity. However, they still suffer from poor stability under high-rate cycling and safety issues, which are mainly induced by the significant growth of Li dendrites and the collapse of the solid electrolyte interphase during extended cycling. Effective protective coatings can withstand severe environmental corrosion during handling and cycling. In this study, we develop a convenient and controllable surface fluorination process to develop a dense and uniform ultrathin lithium fluoride (LiF) protective coating on the Li metal surface by vacuum evaporation. Advanced comprehensive analyses demonstrate that the 200 nm-thick LiF protective coating provides sufficient Li ion transmission channels for efficient transport. This reinforces the structural integrity to withstand volume changes during Li plating/stripping. The highly conformal LiF protective coating minimizes corrosion reactions with carbonate electrolytes and inhibits dendrite formation. Dendrite-free deposition is realized at a high current density of 3 mA cm-2. LiF@Li|LiFePO4 full cells with a 200 nm LiF-coated Li anode exhibit up to 85.31% capacity retention over 600 cycles. Stable Li deposition is achieved for 1200 h under lean electrolyte conditions using a 200-nm LiF-coated Li anode. The developed protective coating shows excellent stabilizing effects on Li anodes and is expected to facilitate the optimization and practical application of Li metal anodes with sufficient interphase stability.