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|LiNi_0.8Mn_0.1Co_0.1O₂ (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.