Computational Screening of Na 3 MBr 6 Compounds as Sodium Solid Electrolytes

作者：Rui Li, Kaiqi Xu, Kaining Liu, Rui Si, Zhizhen Zhang · 发表于：Chemistry of Materials · 年份：2022 · DOI：10.1021/acs.chemmater.2c01966 · 被引用次数：33 · 研究领域：Advanced Battery Materials and Technologies、Advancements in Battery Materials、Thermal Expansion and Ionic Conductivity

All-solid-state batteries (ASSBs) based on metallic Na have received an upsurge of interest in the past few years owing to the low cost of Na resources combined with enhanced safety compared to conventional liquid lithium-ion batteries. Solid electrolytes (SEs) serve as the central of ASSBs as they, together with the composite cathode layer, largely determine the power density, energy density, and cycling performance of ASSBs. Among the several categories of SE materials, halides are considered one of the most promising candidates due to their favorable combination of high ionic conductivity and chemical/electrochemical stability against high-voltage cathode materials. Excellent examples have been demonstrated by lithium halides, while their sodium counterparts have been less explored. Herein, we evaluate the phase stability, electrochemical stability, and conducting property of a series of Na-based bromides Na 3 MBr 6 with the joint utilization of density functional theory calculations, the bond valence site energy (BVSE) method, and ab initio molecular dynamics (AIMD) simulations. Our computations reveal that Na 3 MBr 6 could crystallize in three structures, trigonal P 3̅1 c, monoclinic P 2 1 / n, and trigonal R 3̅ phases, with the structural preference highly related to the type and ionic radii of the M cations. The BVSE and AIMD suggest that the P 3̅1 c phase exhibits a higher conductivity and lower migration barrier than P 2 1 / n and R 3̅ phases. With the introduction o...