Localized Water-In-Salt Electrolyte for Aqueous Lithium-Ion Batteries

Water-in-salt (WIS) electrolytes using super-concentrated organic lithium (Li) salts are of interest for aqueous Li-ion batteries. However, the high salt cost, high viscosity, poor wettability, and environmental hazards remain a great challenge. Herein, we present a localized water-in-salt (LWIS) electrolyte based on low-cost lithium nitrate (LiNO₃ ) salt and 1,5-pentanediol (PD) as inert diluent. The addition of PD maintains the solvation structure of the WIS electrolyte, improves the electrolyte stability via hydrogen-bonding interactions with water and NO₃ ^- molecules, and reduces the total salt concentration. By in situ gelling the LWIS electrolyte with tetraethylene glycol diacrylate (TEGDA) monomer, the electrolyte stability window can be further expanded to 3.0 V. The as-developed Mo₆ S₈ |LWIS gel electrolyte|LiMn₂ O₄ (LMO) batteries delivered outstanding cycling performance with an average Coulombic efficiency of 98.53 % after 250 cycles at 1 C.