Achieving Ultra-Thin Solid Electrolyte Interphase for High-Performance Lithium Metal Anodes via Chloride-Assisted Electrochemical Corrosion.

The thickness and composition of the solid electrolyte interphase (SEI) on lithium (Li) metal are critical factors influencing dendrite growth. This study introduces a novel electrolyte selection strategy based on electrochemical corrosion principles. By employing LiCl and LiNO3 simultaneously, the electrolyte itself has a high donor number, low desolvation energy, high Li⁺ transference number and conductivity, and a moderate electrochemical stability window. In addition, it dynamically reduces the SEI thickness and reactivates dead Li, forming a ≈100 nm SEI enriched with LiF and Li2O on Li metal anode, which ensures the stable cycling of Li symmetric cells for 2000 h at a current density of 5 mA cm⁻2. Consequently, Li metal cells using LiFePO4 (LFP) as the cathode with the LiNO3-LiCl-added electrolyte exhibit excellent cycling performance for 1600 cycles at 680 mA g⁻1. Even with a thin Li metal anode, the Li (5 µm)|LFP cell retains 95% capacity after 70 cycles at 170 mA g⁻1. The universality and feasibility of this electrolyte design are also validated in diverse battery chemistries such as anode-free Cu|LFP, Li|LiNi0.8Mn0.1Co0.1O2 (NMC811), and Li|S cells, as well as in pouch cells with high-loading LFP and NMC811 cathodes, showcasing the promising electrolyte design strategy for Li metal batteries.