Experimental and Computational Analysis of the Solvent-Dependent O[subscript 2]/Li+-O[subscript 2][superpscript −] Redox Couple: Standard Potentials, Coupling Strength, and Implications for Lithium-Oxygen Batteries

Abstract

Understanding and controlling the kinetics of O[subscript 2] reduction in the presence of Li+-containing aprotic solvents, to either Li+-O[subscript 2]− by one-electron reduction or Li[subscript 2]O[subscript 2] by two-electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li-O[subscript 2] batteries. Standard potentials of O[subscript 2]/Li+-O[subscript 2]− and O[subscript 2]/O[subscript 2]− were experimentally measured and computed using a mixed cluster-continuum model of ion solvation. Increasing combined solvation of Li+ and O[subscript 2]− was found to lower the coupling of Li+-O[subscript 2]− and the difference between O[subscript 2]/Li+-O[subscript 2]− and O[subscript 2]/O[subscript 2]− potentials. The solvation energy of Li+ trended with donor number (DN), and varied greater than that of O[subscript 2]− ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li+-O[subscript 2]− solubility and DN. These results highlight the importance of the interplay between ion–solvent and ion–ion interactions for manipulating the energetics of intermediate species produced in aprotic metal–oxygen batteries.