Ab Initio Molecular Dynamics Study of the Effect of Lithium Salts on Lithium Superoxide Clustering in Lithium-Air Batteries*

Lithium-air batteries are an active area of research because of their potential to have a much higher energy density than traditional lithium-ion batteries. However, they are not yet commercially viable due to poor efficiency, high charging voltages, and low cycle lifetimes. Experimental studies of Li-air batteries with aprotic solvents have shown that the O₂ reduction starts when superoxide (O₂^-) forms in solvent and reacts with Li⁺ to form lithium superoxide (Li⁺-O₂^-). Solid Li₂O₂ then forms as the final discharge product on the cathode. Recent experimental work has suggested that a better understanding of the factors governing the behavior of the lithium superoxide in solvent could help control the discharge at the cathode. We are therefore modeling systems of lithium salts and LiO₂ molecules in various common solvents such as dimethyl sulfoxide, acetonitrile, and 1,2-dimethoxyethane to examine how the interplay between solvents and salts affects properties such as LiO₂ clustering behavior. Results from these explicit solvent calculations performed using density functional theory calculations and ab-initio molecular dynamics simulations will be presented and discussed.