Enhancing Lithium Metal Battery Performance Through Reaction Center Shifting in Partially Fluorinated Electrolytes with Localized High Anion Concentration

The design of a compatible electrolyte is crucial for achieving long-lifespan in lithium-metal batteries (LMBs). In this study, we report on a partially fluorinated electrolyte characterized by a weak solvation interaction of Li+ and a localized high anion concentration in the first solvation shell. This unique solvation structure shifts the reaction centers from solvent molecules to anions, enabling the predominant participation of anions in the formation of a LiF-rich solid-electrolyte interphase (SEI). Electrochemical experiments demonstrate efficient Li+ transfer kinetics, reduced Li nucleation overpotential polarization (28 mV), and extended cycling life in Li||Li cells using the partially fluorinated electrolyte. When tested in Li||NCM811 cells, the designed electrolyte delivers a capacity retention of 89.30% and exhibits a high average Coulombic efficiency of 99.80% over 100 cycles with a charge-potential cut-off of 4.6 V vs. Li/Li+ under the current density of 0.4 C. Furthermore, even at a current density of 1C, the cells maintain 81.90% capacity retention and a high average Coulombic efficiency of 99.40% after 180 cycles. This work underscores the significance of weak-solvation interaction in partially fluorinated electrolytes and highlights the crucial role of solvent structure in enabling the long-term stability and high-energy density of LMBs.