Effect of Ce(III) Additives on Positive Electrode Reactions in Li–O₂ Secondary Batteries: Overvoltage Reduction and Mechanistic Divergence

The development of lightweight, high-energy-density secondary batteries is crucial for advancing applications such as electric vehicles and drones. Lithium–oxygen batteries (LOBs), which utilize O2 as an active material, can potentially overcome the theoretical energy density limits of lithium-ion batteries. However, challenges such as high charging overvoltages and degradation of electrodes and electrolytes hinder their practical use. In this study, we investigate the effects of Ce(III) ion additives in amide-based electrolytes on the discharge and charge overvoltages of LOBs. The addition of Ce(III) significantly reduces the particle size of the resulting Li2O2. In addition, mechanistic analysis suggests that Ce(III) acts as a Lewis acid, facilitating the dissolution of Li2O2 into the electrolyte, which subsequently lowers the charging voltage. Thus, through multiple mechanisms, Ce(III) ions in the electrolyte effectively reduce the overvoltage in the charge processes. The insights obtained from evaluating the effects of Ce(III) ion additives are expected to provide a foundation for developing strategies to reduce the charging voltage of LOBs in the future.