Anisotropic Li diffusion in pristine and defective ZnO

TL;DR

This study uses first-principles calculations to analyze how different point defects in ZnO influence lithium diffusion, revealing that oxygen vacancies can enhance Li mobility while zinc vacancies may trap Li.

Contribution

It provides detailed insights into the effects of specific point defects on Li diffusion barriers in ZnO using DFT and NEB methods, highlighting the role of oxygen vacancies.

Findings

Ovac and Znvac lower Li diffusion energy barriers.

Li may be trapped by Znvac, forming LiZn defects.

Ovac enhances Li diffusion kinetics in ZnO.

Abstract

We study the Li interstitial diffusion in pristine and defective ZnO bulk by means of first-principles density functional theory (DFT) coupled with Nudged Elastic Band (NEB) calculations. We consider three types of point defects, i.e., oxygen vacancy (Ovac), Zn vacancy (Znvac) and ZnO vacancy pair (ZnOvac-pair) and investigate their individual effect on the energy barrier of Li interstitial diffusion. Our results predict that Ovac and Znvac lower the Li diffusion energy barrier as compared to the pristine ZnO case. However, we further find that Li interstitial on the other hand may possibly be trapped inside the Znvac subsequently forming the LiZn substitutional type of defect. The similar behavior also observed for Li interstitial in the vicinity of Zn-Ovac_pair though with less change of Li diffusion barriers as compared to the other two cases. Our results indicate that among the three considered defects only Ovac shows possible enhancement of the kinetics of Li diffusion inside ZnO bulk.