Na3MBr6 化合物作为钠固体电解质的计算筛选,Chemistry of Materials

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Na3MBr6 化合物作为钠固体电解质的计算筛选
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-09-08 , DOI: 10.1021/acs.chemmater.2c01966
Rui Li ₁ , Kaiqi Xu ₂ , Kaining Liu _{1,

2} , Rui Si ₁ , Zhizhen Zhang ₁

Affiliation

与传统的液态锂离子电池相比，基于金属钠的全固态电池 (ASSB) 在过去几年中受到了极大的关注，因为钠资源成本低且安全性更高。固体电解质 (SE) 是 ASSB 的核心，因为它们与复合阴极层一起在很大程度上决定了 ASSB 的功率密度、能量密度和循环性能。在几类 SE 材料中，卤化物被认为是最有前途的候选材料之一，因为它们具有高离子电导率和对高压正极材料的化学/电化学稳定性的良好组合。卤化锂已经证明了很好的例子，而钠对应物的探索较少。在这里，我们评估相位稳定性，₃ MBr ₆与密度泛函理论计算、键价位能量 (BVSE) 方法和从头算分子动力学 (AIMD) 模拟的联合利用。我们的计算表明，Na ₃ MBr ₆可以以三种结构结晶，即三角P 3̅1 c、单斜P 2 ₁ / n和三角R 3 ̅ 相，其结构偏好与 M 阳离子的类型和离子半径高度相关。BVSE 和 AIMD 表明P 3̅1 c相表现出比P 2更高的电导率和更低的迁移势垒₁ / n和R 3̅ 相。随着 Na 空位的引入，电导率显着提高，在室温下产生 0.70 mS cm ^{-1的高外推电导率。}此外，还评估了对正极材料的热力学稳定性和化学稳定性。我们的工作提供了对溴化钠的基本理解的见解，并指出了这一系列材料作为 ASSB 中 SE 材料潜在候选者的重要性。

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Computational Screening of Na3MBr6 Compounds as Sodium Solid Electrolytes

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 Na₃MBr₆ 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 Na₃MBr₆ could crystallize in three structures, trigonal P3̅1c, monoclinic P2₁/n, and trigonal R3̅ phases, with the structural preference highly related to the type and ionic radii of the M cations. The BVSE and AIMD suggest that the P3̅1c phase exhibits a higher conductivity and lower migration barrier than P2₁/n and R3̅ phases. With the introduction of Na vacancies, a significant enhancement in the conductivity was achieved, giving rise to a high extrapolated conductivity of 0.70 mS cm^–1 at room temperature. In addition, the thermodynamic stability and chemical stability against cathode materials were also assessed. Our work provides insights into the fundamental understanding of sodium bromides and points to the importance of this family of materials to be used as potential candidates for SE materials in ASSBs.

更新日期：2022-09-08

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