Interphase Engineering via Solvent Molecule Chemistry for Stable Lithium Metal Batteries

Abstract Lithium metal battery has been regarded as promising next‐generation battery system aiming for higher energy density. However, the lithium metal anode suffers severe side‐reaction and dendrite issues. Its electrochemical performance is significantly dependant on the electrolyte components and solvation structure. Herein, a series of fluorinated ethers are synthesized with weak‐solvation ability owing to the duple steric effect derived from the designed longer carbon chain and methine group. The electrolyte solvation structure rich in AGGs (97.96 %) enables remarkable CE of 99.71 % (25 °C) as well as high CE of 98.56 % even at −20 °C. Moreover, the lithium‐sulfur battery exhibits excellent performance in a wide temperature range (−20 to 50 °C) ascribed to the modified interphase rich in LiF/LiO2. Furthermore, the pouch cell delivers superior energy density of 344.4 Wh kg−1 and maintains 80 % capacity retention after 50 cycles. The novel solvent design via molecule chemistry provides alternative strategy to adjust solvation structure and thus favors high‐energy density lithium metal batteries.