Molecular Dynamics with Different Equilibration Methods for Modeling Solvent - Lithium Salt Systems 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. In Li-air batteries, O₂ reduction starts when superoxide forms in solvent and reacts with Li⁺ to form lithium superoxide (LiO₂). Solid Li₂O₂ then forms as the final discharge product on the cathode. Recent experimental work suggests that the choice of solvent and the presence of lithium salts in the system may have a large impact on how the discharge product forms at the cathode. We therefore modeled the clustering of lithium salt molecules in solvent without LiO₂ present with explicit solvent calculations using both classical and ab initio molecular dynamics simulations. For each ab initio simulation, we also used one of two equilibration procedures: (1) performing a classical molecular dynamics simulation or (2) performing shorter ab initio simulations at higher temperatures. A comparison of these computational approaches for properties such as coordination numbers will be presented.