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 over-potential. 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.

Automated summary

This study found that using the tri-functional additive IMPBr can solve the slow kinetics problem of ORR and OER in Li-O-2 batteries, as well as protect the lithium metal anode. It has the ability to bind with O-2(-) and Li+ and serves as a catalyst for decomposition and prevention of solvents and side reactions during discharge and charge processes. The synergy effect of IMP+ and Br- can improve the cycle and rate performance of the battery.