First-principles simulations of Li boracites Li4B7O12Cl and Li5B7O12.5Cl
First-principles simulations of Li boracites Li4B7O12Cl and Li5B7O12.5Cl
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DOI：
10.1103/physrevmaterials.6.025401
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发表时间：
2022-02
影响因子：
3.4
通讯作者：
Yan Li;N. Holzwarth
中科院分区：
文献类型：
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作者：
Yan Li;N. Holzwarth
艾德认为，硼酸锂晶体是一种很有前途的离子导体，可用于全固态电池。借助第一性原理建模技术，我们能够证明这些材料具有天然间隙位点的结构，这些结构在锂离子迁移过程中起着重要作用。这些自然间隙网站的安排遵循群论分析的计算和实验分析的结构。具体地说，计算的低温α相Li 4 B O 12 Cl具有面心菱面体R3 c结构，这与每个传统晶胞具有24个自然间隙位的理想面心立方F <$43c结构密切相关。锂离子在这种材料中的扩散被发现主要是通过一个协调一致的运动，涉及这些填隙网站和两个相邻的主机晶格网站，与该材料的大测量的离子电导率一致。在Li 4 B 7 O 12 Cl中每分子式单元加一个Li 2 O簇形成Li 5 B 7 O 12 . 5 Cl，以面心立方F 23结构结晶，F <$43 c结构的一个子群。虽然这些F 23晶体每个常规晶胞具有16个天然间隙位点，但它们的分布使得它们不参与Li离子扩散机制，这与针对该材料测量的可忽略的离子电导率一致。Li 4 B 7 O 12 Cl R 3 c结构和Li 5 B 7 O 12的声子谱分析。结果表明，两种晶体都是动力学稳定的.这些材料的化学稳定性通过Li 4 B 7 O 12 Cl和Li 5 B 7 O 12的凸船体分析来表示。5 Cl相对于它们的结构单元LiCl、Li 2 O和B 2 O 3。
Lithium boracite crystals have been identified as promising ion conductors for possible use in all-solid-state batteries. With the help of first-principles modeling techniques, we are able to show that these materials have structures with natural interstitial sites which play important roles in Li ion migration processes. The arrangements of these natural interstitial sites follow from group theory analyses of the computed and experimentally analyzed structures. Specifically, the low-temperature α phase of Li 4 B 7 O 12 Cl is computed to have the face-centered rhombohedral R 3 c structure which is closely related to an ideal face-centered cubic F ¯43 c structure with 24 natural interstitial sites per conventional unit cell. Li ion diffusion in this material is found to proceed largely by a concerted motion involving these interstitial sites and two neighboring host lattice sites, consistent with the large measured ionic conductivity of this material. Adding one addition Li 2 O cluster per formula unit to Li 4 B 7 O 12 Cl forms Li 5 B 7 O 12 . 5 Cl, which crystallizes in the face-centered cubic F 23 structure, a subgroup of the F ¯43 c structure. While these F 23 crystals have 16 natural interstitial sites per conventional unit cell, their distribution is such that they do not participate in Li ion diffusion mechanisms, as is consistent with the negligible ionic conductivity measured for this material. Phonon spectral analyses of Li 4 B 7 O 12 Cl in its R 3 c structure and Li 5 B 7 O 12 . 5 Cl in its F 23 structure show that both crystals are dynamically stable. Chemical stability of these materials is indicated by convex hull analysis of Li 4 B 7 O 12 Cl and Li 5 B 7 O 12 . 5 Cl with respect to their building blocks of LiCl, Li 2 O, and B 2 O 3 .