Ultra‐Low Content Triethylammonium Chloride Facilitates Localized High‐Concentration Electrolytes and Formation of Inorganic Solid Electrolyte Interface

Localized high‐concentration electrolytes offer a potential solution for achieving uniform lithium deposition and a stable solid‐electrolyte interface in Lithium metal batteries. However, the use of highly concentrated salts or structure‐loaded diluents can result in significantly higher production costs and increased environmental burdens. Herein, a novel localized high‐concentration electrolyte is developed, comprising ultra‐low content (2% by mass) triethylammonium chloride as an electrolyte additive. The stable Lewis acid structure of the triethylammonium chloride molecule allows for the adsorption of numerous solvent molecules and TFSI− anions, intensifying the electrostatic interactions between lithium ions and anions. The chloride ions introduced by TC, along with TFSI− anions, integrate into the solvent sheath, forming a LiCl‐rich inorganic SEI and enhancing the electrochemical performance of the lithium metal anode. The improved Li||Li cell shows excellent cycling stability for over 500 h at 1 mA cm2 with a 27 mV overpotential. This work provides insights into the impact of electrolyte additives on the electrode‐electrolyte interface and Li‐ion solvation, crucial for safer lithium metal battery development.