Identifying migration channels and bottlenecks in monoclinic NASICON-type solid electrolytes with hierarchical ion-transport algorithms

Abstract

Monoclinic natrium superionic conductors (NASICON; Na3Zr2Si2PO12) are well-known Na-ion solid electrolytes which have been studied for 40 years. However, due to the low symmetry of the crystal structure, identifying the migration channels of monoclinic NASICON accurately still remains unsolved. Here, a cross-verified study of Na+ diffusion pathways in monoclinic NASICON by integrating geometric analysis of channels and bottlenecks, bond-valence energy landscapes analysis, and ab initio molecular dynamics simulations is presented. The diffusion limiting bottlenecks, the anisotropy of conductivity, and the time and temperature dependence of Na+ distribution over the channels are characterized and strategies for improving both bulk and total conductivity of monoclinic NASICON-type solid electrolytes are proposed. This set of hierarchical ion-transport algorithms not only shows the efficiency and practicality in revealing the ion transport behavior in monoclinic NASICON-type materials but also provides guidelines for optimizing their conductive properties that can be readily extended to other solid electrolytes. © 2021 Wiley-VCH GmbH