Designing Temperature-Insensitive Solvated Electrolytes for Low-Temperature Lithium Metal Batteries

Lithium metal batteries face problems from sluggish charge transfer at interfaces, as well as parasitic reactions between lithium metal anodes and electrolytes, due to the strong electronegativity of oxygen donor solvents. These factors constrain the reversibility and kinetics of lithium metal batteries at low temperatures. Here, a nonsolvating cosolvent is applied to weaken the electronegativity of donor oxygen in ether solvents, enabling the participation of anionic donors in the solvation structure of Li+. This strategy significantly accelerates the desolvation process of Li+ and reduces the side effects of solvents on interfacial transport and stability. The designed anion-aggregated electrolyte has a unique temperature-insensitive solvation structure and enables lithium metal anodes to achieve a high average Coulombic efficiency at room temperature and −20 °C. A high-loading LiFePO4||Li cell exhibited high reversibility with a 100% capacity retention after 150 cycles at room temperature, −20, and −40 °C. The practical 1 Ah-level LiFePO4||Li pouch-cell delivered 81% and 61% of the capacity at room temperature when charged and discharged at −20 and −40 °C, respectively. This strategy of constructing temperature-insensitive solvation by electronegativity regulation offers a novel approach for developing electrolytes of low-temperature batteries.