NaAlCl₄ is an established solid electrolyte in high-temperature Na-based battery systems, but its ionic conductivity is not sufficiently high for room-temperature applications. We employ density functional theory and thermodynamic corrections to evaluate the efficacy of various elements for substitution, utilizing on-the-fly machine-learned potentials to accelerate the required phonon calculations by 1 order of magnitude at a minor error of −0.7 ± 1.0 meV/atom. All investigated isovalent substitutions are favorable within 4 meV/atom, with potassium and silver as substitutes for sodium and gallium as a substitute for aluminum. The most promising aliovalent substitution was identified for Zn on the tieline between NaAlCl₄ and Na₂ZnCl₄. The structure of latter, with aluminum ions replacing zinc, yields a structure with separate layers for the differently charged cations and vacancies for potential Na conduction. Our investigation may pave the way for more reliable discovery of new Na conductors by inclusion of thermodynamic properties.

中文翻译：

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用密度泛函理论探索固体电解质 NaAlCl4 中的阳离子取代


NaAlCl₄ 是高温钠基电池系统中已建立的固体电解质，但其离子电导率对于室温应用来说不够高。我们采用密度泛函理论和热力学校正来评估各种元素的取代功效，利用动态机器学习电位以 -0.7 ± 1.0 meV/原子的小误差将所需的声子计算加速 1 个数量级。所有研究的等价取代在 4 meV/原子以内都是有利的，其中钾和银是钠的替代品，镓是铝的替代品。最有希望的同构价取代是在 NaAlCl₄ 和 Na₂ZnCl₄ 之间的连接线上确定的 Zn。后者的结构，用铝离子代替锌，产生了一个结构，该结构具有不同电荷的阳离子和潜在 Na 传导的空位。我们的研究可能通过包含热力学特性为更可靠地发现新的 Na 导体铺平道路。