Tuning solid electrolyte interface against oxygen/superoxide-derived attack on Li-metal anode in Li-O2 battery

Abstract

Practical working environment (O2-saturated base electrolyte), architecture and operation mechanism/processes of Li-O2 batteries (LOBs) endows severe O2 and superoxide (O2-)-derived attack on Li-metal and solid electrolyte interface (SEI) at Li/electrolyte interface, limiting stability of Li anodes and LOBs. Herein, how O2/O2--derived attack on Li-metal and structure/composition of SEI are revealed by cryogenic transmission electron microscopy (cryo-TEM) and comprehensive spectroscopic characterizations. Specifically, generated from O2-reduction on Li-anode, the Li2O-induced nucleophilic attack on base electrolyte decomposition and Li corrosion especially during long-term aging, and more aggressive O2- created in cycling aggravates Li anodes and SEI. Moreover, to address O2/O2--derived attack on Li-metal, 1, 2-difluorobenzene (F-ben) was introduced as cosolvent in base electrolyte to make an F-ben electrolyte, in which F-ben preferentially reacted with Li-metal to form dual-functional SEI. Tuned SEI not only separate Li2O from bulk electrolyte thus suppresses O2-derived chemical attack, also acts as protective film protecting Li-metal against O2- attack. Eventually, electro-stability/reversibility of Li-metal in practical working environment of LOBs and battery performance of LOBs are significantly enhanced with help of F-ben cosolvent. This work sheds light on behavior of O2/O2--derived attack on Li-metal and SEI, sets an effective and practicable path towards practical applications of LOBs.