Fluorosulfonyl Additive-Reinforced Interphases for High-Voltage and Fast-Charging Lithium Metal Batteries

Electrolytes capable of simultaneously stabilizing lithium metal anodes and high-nickel cathodes under high-voltage and high-rate operation are essential for practical lithium metal batteries yet remain difficult to realize. Here, methyl fluorosulfonyldifluoroacetate (MDFSA) is introduced as an electrolyte additive to regulate the Li$^+$ solvation structure in an ether–carbonate co-solvent electrolyte. MDFSA weakens the coordination of 1,2-dimethoxyethane (DME) with Li$^+$ and promotes the involvement of DFOB$^–$ in the solvation sheath, facilitating the formation of robust inorganic-rich interphases at both the lithium metal anode and the cathode. The optimized electrolyte enables Li||LiNi$_{0.91}$Co$_{0.06}$Mn$_{0.03}$O$_2$ cells to deliver 75.8% capacity retention after 500 cycles at 4.5 V and 1 C and 80.53% capacity retention after 500 cycles at 4.3 V and 4 C. These results highlight the effectiveness of fluorosulfonyl additive-enabled solvation and interphase regulation for improving the high-voltage stability, rate capability, and cycling durability of lithium metal batteries.