High-Voltage and Ultralow-Temperature Lithium Metal Batteries Achieved by Methyl Acetate-Based Locally High-Concentration Electrolyte

The instability of the cathode/electrolyte interface and the increased difficulty of lithium-ion desolvation at low temperatures significantly limit the development of rechargeable lithium metal batteries (LMBs). In this work, a local high-concentration electrolyte based on methyl acetate was prepared using the diluent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. Theoretical calculations and experimental results show that optimizing the solvent structure of the electrolyte by adjusting the lithium salt concentration and adding a diluent facilitates the desolvation process of Li+. As a result, the Li/LiCoO2 cell with the optimized 5M-AFDT electrolyte exhibits stable long-term cycling at 4.5 V under room temperature, achieving a capacity retention of 81.1% after 400 cycles at 1 C. In addition, the electrolyte demonstrates outstanding low-temperature performance, allowing the cell to deliver 86.4% of its room-temperature capacity at −40 °C and maintain stable cycling for 100 cycles. This study offers a detailed analysis of the impact of the electrolyte’s solvation structure on battery performance, providing a promising approach for designing electrolytes for low-temperature, high-voltage LMBs.