Imidazolium bromide: A tri-functional additive for rechargeable Li-O2 batteries

High energy density lithium-oxygen (Li-O 2 ) batteries require soluble catalysts to accelerate the kinetics of oxygen reduction/evolution reaction (ORR/OER), and require SEI forming additives to protect lithium metal anode from side reaction with solvents, reduced oxygen species and soluble catalysts. In this study, a tri-functional additives 1-methyl, 3-benzyl, 1H imidazolium bromide (IMPBr) is dissolved in the dimethyl sulfoxide (DMSO)-based electrolyte to solve the problems of the slow dynamic process of ORR and OER, and protect the lithium anode by suppressing the dendrite formation in O 2 atmosphere. During discharging, IMP + has a strong binding ability to the intermediate product O 2 − , and Br − is highly associated with Li + , helping drive the solvation mechanism. During charging, Br − mediates the decomposition of battery discharge products and reduces the charge overpotential. Meanwhile, the positively charged IMP + can be attracted to the surface of the anode via electric attraction, in situ forming a stable SEI layer to prevent DMSO, Br 3 – , and Br 2 from attacking the lithium metal and growth of lithium dendrites. The synergy effect of the IMP + and Br – improves the cycle and rate performance of the Li-O 2 battery.