Non-solvating fluorosulfonyl carboxylate enables temperature-tolerant lithium metal batteries

Abstract

Advanced electrolyte engineering is an important strategy for developing high-efficacy lithium (Li) metal batteries (LMBs). Unfortunately, the current electrolytes limit the scope for creating batteries that perform well over temperature ranges. Here, we present a new electrolyte design that uses fluorosulfonyl carboxylate as a non-solvating solvent to form difluoroxalate borate (DFOB-) anion-rich solvation sheath, to realize high-performance working of temperature-tolerant LMBs. With this optimized electrolyte, favorable SEI and CEI chemistries on Li metal anode and nickel-rich cathode are achieved, respectively, leading to fast Li+ transfer kinetics, dendrite-free Li deposition and suppressed electrolyte deterioration. Therefore, Li||LiNi0.80Co0.15Al0.05O2 batteries with a thin Li foil (50 μm) show a long-term cycling lifespan over 400 cycles at 1C and a superior capacity retention of 90% after 200 cycles at 0.5C under 25 ℃. Moreover, this electrolyte extends the operating temperature from −10 to 30 ℃ and significantly improve the capacity retention and Coulombic efficiency of batteries are improved at high temperature (60 ℃). Fluorosulfonyl carboxylates thus have considerable potential for use in high-performance and all-weather LMBs, which broadens the new exploring of electrolyte design.