Study on the Structure and Transport Properties of Molten Salts of NaF–KF–AlF3 Electrolytes by First-Principles Molecular Dynamics Simulation

IF 1.8 3区化学 Q3 CHEMISTRY, INORGANIC & NUCLEAR Russian Journal of Inorganic Chemistry Pub Date : 2024-04-12 DOI:10.1134/s0036023624600163

Qibo Liu, Laixin Zhang, Hengwei Yan, Zhanwei Liu, Xiumin Chen

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Abstract

The NaF–KF–AlF₃ is a promising low-temperature electrolyte for industrial application. Herein, we used a molecular dynamics and first-principles calculations to simulate NaF–KF–AlF₃ molten salts with molar ratios(n(NaF + KF)/AlF₃) of 1.3–1.6 and 30 mol % NaF at 1123 K. The results of the study reveal the law of influence of molar ratio on the structural properties and transport properties of the NaF–KF–AlF₃ system. The results show that the average coordination number of the NaF–KF–AlF₃ system was about 4.8, and the ionic structure was mainly [AlF₄]^– and [AlF₅]^2–, with strong covalent interactions between Al-F ions. As the molar ratio increased five-coordinated [AlF₅]^2– gradually became the dominant population in the molten salts, and the proportion of bridging fluoride ions increased, promoting ionic polymerization in the molten salts and the formation of complex ionic groups. The order of ion diffusion ability in the molten salts followed the order of K⁺ > Na⁺ > F^– > Al³⁺, when the molar ratio was 1.3 and 1.4, changing to Na⁺ > K⁺ > F^– > Al³⁺, when the molar ratio was 1.5 and 1.6. The viscosities and ionic conductivities of the molten salts were in the range of 1.1–1.65 mPa s, and 0.85–1.15 S/cm, respectively.

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通过第一原理分子动力学模拟研究 NaF-KF-AlF3 电解质熔盐的结构和传输特性

摘要 NaF-KF-AlF3是一种具有工业应用前景的低温电解质。本文采用分子动力学和第一性原理计算方法，模拟了摩尔比（n(NaF + KF)/AlF3 ）为 1.3-1.6 和 NaF 为 30 mol % 的 NaF-KF-AlF3 熔盐在 1123 K 下的结构。结果表明，NaF-KF-AlF3体系的平均配位数约为4.8，离子结构主要为[AlF4]-和[AlF5]2-，Al-F离子之间具有较强的共价相互作用。随着摩尔比的增加，五配位的[AlF5]2-逐渐成为熔盐中的优势种群，架桥氟离子的比例增加，促进了熔盐中的离子聚合，形成复杂的离子基团。当摩尔比为 1.3 和 1.4 时，熔盐中离子扩散能力的顺序为 K+ > Na+ > F- > Al3+，当摩尔比为 1.5 和 1.6 时，则变为 Na+ > K+ > F- > Al3+。熔盐的粘度和离子电导率分别为 1.1-1.65 mPa s 和 0.85-1.15 S/cm。

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来源期刊

Russian Journal of Inorganic Chemistry 化学-无机化学与核化学

CiteScore

3.10

自引率

38.10%

发文量

237

审稿时长

3 months

期刊介绍： Russian Journal of Inorganic Chemistry is a monthly periodical that covers the following topics of research: the synthesis and properties of inorganic compounds, coordination compounds, physicochemical analysis of inorganic systems, theoretical inorganic chemistry, physical methods of investigation, chemistry of solutions, inorganic materials, and nanomaterials.