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首页> 外文期刊>RSC Advances >How does the Li-distribution in the 16d sites determine the stability of A3(Li,Ti5)O12 (A = Li and Na)?
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How does the Li-distribution in the 16d sites determine the stability of A3(Li,Ti5)O12 (A = Li and Na)?

机译：16D位点的锂分布如何确定A3（Li，Ti5）O12（A = Li和Na）的稳定性？

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Li _(3) (Li,Ti _(5) )O _(12) (LTO) is a stable and safe negative electrode material for Li-ion batteries, and its Na substitute Na _(3) (Li,Ti _(5) )O _(12) (NTO) is a counterpart for the Na-ion battery. In LTO and NTO, a sixth of the Ti-sites (16d) in the spinel framework are replaced by Li: Li mixing in the 16d sites. For conducting theoretical studies on these materials, e.g. , density functional theory (DFT) calculations, one has to confront the astronomical number of combinations of Li distribution in 16d sites to construct model structures, of which the size is sufficiently large to represent the bulk material properties. Only a limited number of models, whose structures are a priori specified by “researcher intuition,” have been examined thus far, and how Li-mixing determines the material stability has yet to be clarified. Herein, we statistically analyzed the DFT total energy of more than 2 × 10 ~(4) model structures of LTO and NTO that were extracted from the 4 × 10 ~(8) possible combinations of Li-mixing with computer-aided symmetry analysis and an automated model building system. The local energy analysis further revealed the local stability/instability of each structure. We found that LTO and NTO stability can be well explained by the apparent coulombic repulsion between Li ~(+) in the 16d sites as if they were placed in a matrix of dielectric constants of 1.92 and 2.04 for LTO and NTO, respectively. That is, the sum of the inverse of the Li–Li distance ( S ) serves as a good descriptor in predicting the stability of these materials. The extent to which the O ~(2?) anions are displaced from the Wyckoff position (32e) is considered to differentiate NTO from LTO. However, the electronic structure of NTO does not significantly differ from that of LTO unless S exceeds a certain limit. These results suggest that the spinel framework tolerates the structural instability and variety to some extent, which is important in constructing a spinel structure with the mixing of other cations, thereby replacing the rare element Li.
机译：Li _（3）（Li，Ti _（5））O _（12）（LTO）是锂离子电池的稳定和安全的负极材料，其NA替代NA _（3）（LI，TI _ （5））O _（12）（NTO）是Na离子电池的对应物。在LTO和NTO中，尖晶石框架中的第六个Ti - 位点（16D）被Li：Li在16D位点混合来取代。用于对这些材料进行理论研究，例如， ，密度函数理论（DFT）计算，必须面对16D位点中的LI分布的天文数量，以构建模型结构，其中尺寸足够大以表示散装材料特性。迄今为止，仅研究了“研究人员直觉”规定的有限数量的模型，其结构是由“研究员直觉”规定的先验，以及LI混合如何确定尚未澄清的材料稳定性。在此，我们在统计上分析了LTO和NTO的2×10〜（4）模型结构的DFT总能量，其从4×10〜（8）可以与计算机辅助对称分析和计算机辅助对称分析的组合中提取自动模型构建系统。局部能量分析进一步揭示了每个结构的局部稳定性/不稳定性。我们发现LTO和NTO稳定性可以通过16D位点中的Li〜（+）之间的表观库仑排斥力很好地解释，因为它们分别置于LTO和NTO的1.92和2.04的介电常数的基质中。也就是说，Li-Li距离的倒数的总和用作预测这些材料的稳定性的良好描述符。从Wyckoff位置（32E）移位O〜（2？）阴离子的程度被认为是将NTO与LTO分化。然而，除非S超过一定限制，否则NTO的电子结构与LTO的电子结构没有显着不同。这些结果表明，尖晶石框架在一定程度上耐受结构不稳定性和多样性，这对于用其他阳离子的混合构建尖晶石结构是重要的，从而取代稀有元素Li。

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