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.