First-Principles Study of the Polaron Formation Process in Energy Materials

Abstract

Polaron formation severely limits the conduction properties of many metal oxides utilized in electrochemical energy storage and conversion applications. Thus, to improve the charge performance of such energy devices, it is essential to understand the fundamental stages of polaron formation. In this work, we utilize the HSE06 hybrid functional to study the initial stage of the polaron formation process in a series of metal oxides. By separating out electronic and lattice energy contribution to the formation of electron polarons, we find that polaron formation barrier heights are directly correlated with an electronic relaxation delay, which is determined by the hybridization of the conduction band minimum. Our results indicate that the formation of polarons may be mitigated by suitably engineering the electronic structure of the material, through a delayed electronic relaxation mechanism. Overall, these results point towards a systematic bottom-up approach for engineering the conductivity and overall electrochemical rate performance of metal oxide energy materials.