CsI as Multifunctional Redox Mediator for Enhanced Li–Air Batteries

We introduce CsI as a multifunctional redox mediator to enhance the performance of Li-air batteries. CsI dissolved in the electrolyte is ionized into Cs(+) and I(-), which perform their roles in the Li anode and air electrode, respectively. The I(-) ions in the electrolyte facilitate the dissolution of Li2O2 in the air electrode as a redox mediator, which reduces the overpotential of the cell. The low overpotential also leads to the suppression of parasitic reactions occurring in the high-voltage range, such as the decomposition of the electrolyte and the reaction between Li2O2 and carbon. At the same time, the Cs(+) ions act as an electrostatic shield at the sharp points of the Li anode, hindering the growth of Li dendrite. The combined effects of reduced parasitic reactions and hindered Li-dendrite growth successfully improve the cyclic performance of Li-air cells.