Boosting Fast Charging of Lithium-Metal Batteries via Weak Interactions Between Non-Solvating Solvents and Anions in High-Safety Eutectic Electrolytes

Proper design of the solvation structure is crucial for the development of lithium metal batteries (LMBs). In this paper, the use of 1,2-Dimethoxyethane (DME) as a non-solvating cosolvent in amide-based eutectic electrolytes is proposed to address challenges related to high viscosity, high polarization, and low conductivity, thus enhancing the compatibility with lithium metal anodes. Through physical characterization combined with simulation calculations the existence of a weak interaction between DME and anions is confirmed, which promotes the dissociation of lithium salts and increases the Li+ transference number and diffusion coefficient, thus improving the fast charging performance of eutectic electrolytes. In addition, stable SEI layer enriched with inorganic components is formed during the cycling process, resulting in uniform and dense lithium deposition. The fast charging performance of the cell can be effectively improved by utilizing the interaction between anions and solvents. The LiFePO4 (LFP)||Li cell has a capacity retention of 97% after 1200 cycles at 5 C and also performs well at high temperature of 50 degrees C. Overall, the use of a non-solvating cosolvent in eutectic electrolytes presents a promising and innovative approach for enhancing electrolyte performance in LMBs. An amide-based eutectic electrolyte with non-solvating cosolvent possesses non-flammability, better interfacial stability, wider electrochemical window. The weak interactions between the cosolvent and the anion promote lithium-ion migration. The formation of LiF-LixN-rich SEI layer is flat and dense with dendrite-free, which improves the long cycling stability of fast charging. image