Importance of Equilibration Method and Sampling for <i>Ab Initio</i> Molecular Dynamics Simulations of Solvent - Lithium Salt Systems in Lithium-Oxygen Batteries

Lithium-oxygen batteries have a higher energy densities than traditional lithium-ion batteries. However, they are not yet commercially viable due to poor efficiency, high charging voltages, and low cycle lifetimes. These issues could be addressed with a deeper fundamental understanding of the atomistic behavior of these batteries. One tool to model such atomic scale behavior is ab initio molecular dynamics (AIMD) simulations. However, AIMD simulations are limited to timescales of tens of picoseconds. As a result, equilibration and sampling methodologies can have a significant effect on the behavior of AIMD simulations. We thus compared two equilibration methods for AIMD simulations of systems of common solvents and salts found in lithium-oxygen batteries: (1) using an AIMD temperature ramp and (2) using a classical MD simulation followed by a short AIMD simulation all at 300 K. I will discuss how the differences between our simulation results and experimental results for properties such as coordination number illustrate the importance of both equilibration method and independent sampling for extracting experimentally relevant quantities from AIMD simulations.