Evaluation of Amorphous Oxide Coatings for High-Voltage Li-Ion Battery Applications Using a First-Principles Framework

Abstract

Surface coatings can effectively suppress cathode degradation and enhance electrochemical performance of lithium-ion batteries. To improve our understanding and rational design of amorphous cathode coating materials, here, we present a framework to explore transport mechanisms and thermodynamic stability in such materials. The framework includes series of ab-initio molecular dynamics (AIMD) simulations to obtain amorphous structures and diffusion trajectories, the analysis of the change in coordinating environments during diffusion, the estimation of room temperature diffusivities and the evaluation of the material's suitability in terms of its ability to facilitate Li+ transport while blocking O2- transport. We apply this framework to two commonly used amorphous coating materials: ZnO and Al2O3. We find that (1) Li+ and O2- diffuse much faster in ZnO than in Al2O3. (2) At a state of high charge, neither Al2O3 nor ZnO is expected to retain a significant amount of Li+. (3) Al2O3 provides a better conformal cathode coating than ZnO. We believe this framework can be productively used to evaluate other amorphous materials for different performance metrics and facilitate the development of optimal cathode coatings.