Optimizing Electrode/Electrolyte Interphases and Li-ion Flux/Solvation with Qua-functional Heptafluorobutyric Anhydride.

The safety and electrochemical performance of rechargeable lithium-metal batteries (LMBs) are primarily influenced by the additives in the organic liquid electrolytes. However, multi-functional additives are still rarely reported. Herein, we proposed heptafluorobutyric anhydride (HFA) as a qua-functional additive to optimize the composition and structure of the solid electrolyte interphase (SEI) at the electrode/electrolyte interface. The reduction/oxidation decomposition of the fluorine-rich HFA facilitate uniform inorganic-rich SEI and compact cathode electrolyte interphase (CEI) formation, which enables stable lithium plating during charge and suppresses the dissolution of transition-metal ions. Moreover, HFA optimizes the Li-ion solvation for stable Li plating/stripping and serves as the surfactant to enhance the wettability of the separator by the electrolyte to increase Li-ion flux. The symmetric Li||Li cell with 1.0 wt% HFA electrolyte had an excellent cycling performance over 340 h at 1.0 mA cm-2 with a capacity of 0.5 mAh cm-2 while the Li||NCM622 cell maintained high capacity retention after 250 cycles and outstanding rate performance even at 15C.