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

High energy density lithium-oxygen (Li-O₂) 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 O₂ atmosphere. During discharging, IMP⁺ has a strong binding ability to the intermediate product O₂⁻, 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, Br₃^–, and Br₂ 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-O₂ battery.