Crystal Structures, Local Atomic Environments, and Ion Diffusion Mechanisms of Scandium-Substituted Sodium Superionic Conductor (NASICON) Solid Electrolytes,Chemistry of Materials

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Crystal Structures, Local Atomic Environments, and Ion Diffusion Mechanisms of Scandium-Substituted Sodium Superionic Conductor (NASICON) Solid Electrolytes
Chemistry of Materials ( IF 7.2 ) Pub Date : 2018-03-23 00:00:00 , DOI: 10.1021/acs.chemmater.7b05237
Yue Deng _{1,

2,

3,

4} , Christopher Eames ₂ , Long H. B. Nguyen ₅ , Oliver Pecher ₅ , Kent J. Griffith ₅ , Matthieu Courty ₁ , Benoit Fleutot _{1,

3,

4} , Jean-Noël Chotard _{1,

4} , Clare P. Grey _{3,

5} , M. Saiful Islam _{2,

3} , Christian Masquelier _{1,

3,

4}

Affiliation

The importance of exploring new solid electrolytes for all-solid-state batteries has led to significant interest in NASICON-type materials. Here, the Sc³⁺-substituted NASICON compositions Na₃Sc_xZr_2–x(SiO₄)_2–x(PO₄)_1+x (termed N3) and Na₂Sc_yZr_2–y(SiO₄)_1–y(PO₄)_2+y (termed N2) (x, y = 0–1) are studied as model Na⁺-ion conducting electrolytes for solid-state batteries. The influence of Sc³⁺ substitution on the crystal structures and local atomic environments has been characterized by powder X-ray diffraction (XRD) and neutron powder diffraction (NPD), as well as solid-state ²³Na, ³¹P, and ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. A phase transition between 295 and 473 K from monoclinic C2/c to rhombohedral R3̅c is observed for the N3 compositions, while N2 compositions crystallize in a rhombohedral R3̅c unit cell in this temperature range. Alternating current (AC) impedance spectroscopy, molecular dynamics (MD), and high temperature ²³Na NMR studies are in good agreement, showing that, with a higher Sc³⁺ concentration, the ionic conductivity (of about 10^–4 S/cm at 473 K) decreases and the activation energy for ion diffusion increases. ²³Na NMR experiments indicate that the nature of the Na⁺-ion motion is two-dimensional on the local atomic scale of NMR although the long-range diffusion pathways are three-dimensional. In addition, a combination of MD, bond valence, maximum entropy/Rietveld, and van Hove correlation methods has been used to reveal that the Na⁺-ion diffusion in these NASICON materials is three-dimensional and that there is a continuous exchange of sodium ions between Na(1) and Na(2) sites.

中文翻译：

Scan取代的钠超离子导体（NASICON）固体电解质的晶体结构，局部原子环境和离子扩散机理

探索用于全固态电池的新型固体电解质的重要性已引起人们对NASICON型材料的极大兴趣。在此，Sc ³⁺取代的NASICON组成为Na ₃ Sc _x Zr _{2– x}（SiO ₄）_{2– x}（PO ₄）_{1+ x}（称为N3）和Na ₂ Sc _y Zr _{2– y}（SiO ₄）_{1 – y}（PO ₄）_{2+ y}（称为N2）（x，y = 0–1）作为模型Na ⁺进行研究固态电池的离子导电电解质。Sc ³⁺取代对晶体结构和局部原子环境的影响已通过粉末X射线衍射（XRD）和中子粉末衍射（NPD）以及固态²³ Na，³¹ P和²⁹ Si表征核磁共振（NMR）光谱。从单斜晶295和473 K的一个相转变Ç 2 / ç到菱形- [R 3 Ç被观察到N3组合物中，而组合物N2在菱面体结晶- [R 3 Ç在此温度范围内的晶胞。交流电（AC）阻抗谱，分子动力学（MD）和高温²³ Na NMR研究非常吻合，表明在较高的Sc ³⁺浓度下，离子电导率（约10 ^–4 S / cm 473 K）减少，而离子扩散的活化能增加。²³ Na NMR实验表明，Na ⁺离子运动的性质在NMR的局部原子尺度上是二维的，尽管长程扩散途径是三维的。此外，MD，键价，最大熵/ Rietveld和van Hove相关方法的组合已被用于揭示Na ⁺离子在这些NASICON材料中的扩散是三维的，并且Na（1）和Na（2）位置之间存在钠离子的连续交换。

更新日期：2018-03-23

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