Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
ACS Appl Mater Interfaces. 2023 May 3;15(17):21086-21096. doi: 10.1021/acsami.3c01570. Epub 2023 Apr 23.
Due to the excellent ionic conductivity and compatibility with high-voltage cathodes, halide-based superionic conductors as promising electrolytes have received widespread attention. A series of halide-based conductors, including NaYCl, are investigated aiming to find new solid electrolytes for sodium-ion batteries. However, NaYCl with high ionic conductivity is meta-stable in thermostability while the stable phase exhibits poor ionic transport properties. In this work, we find that the coplanar formed anionic group (YCl) is the result of a combination of the structural features of the fast ion phase and stable phase of NaYCl by systematic analysis of crystal structures. Aiming to find fast sodium-ion conductors, the three-step structure construction method using functional (YCl) groups as building blocks is proposed, and three new crystal structures in the composition of NaYCl with the space group of P6, Cc, and R32 are obtained. Na transport properties, thermostability, and electrochemical window of these structures with various symmetries are investigated by first-principles calculation methods. The results show that the principle to inverse design crystal structures of halides by basic blocks, e.g., anion groups and mobile cations, is proven to be effective and successful. For P6-NaYCl with outstanding transport properties, the simulation results indicate that its superionic behavior is attributed to the coherent diffusion connecting two directions. The synchronization of the migration pathways along the plane and the migration pathways along the direction promotes the Na ion conductivity in NaYCl. Our research will promote the understanding of the transport mechanism in halide-based electrolytes, and the structure construction method based on functional basic building blocks and special stacking modes will accelerate the inverse design of inorganic crystal structures.
由于卤化物基超离子导体具有优异的离子导电性和与高压阴极的相容性，作为有前途的电解质受到了广泛关注。本研究旨在寻找新型钠离子电池固体电解质，对一系列卤化物基导体，包括 NaYCl，进行了研究。然而，具有高离子电导率的 NaYCl 在热稳定性方面亚稳，而稳定相表现出较差的离子输运性能。在这项工作中，通过对晶体结构的系统分析，我们发现共面形成的阴离子基团 (YCl) 是 NaYCl 快离子相和稳定相结构特征的结合体。为了寻找快速钠离子导体，提出了使用功能 (YCl) 基团作为构建块的三步结构构建方法，并获得了具有空间群 P6、Cc 和 R32 的 NaYCl 组成的三种新晶体结构。通过第一性原理计算方法研究了这些具有不同对称性的结构的钠离子输运性能、热稳定性和电化学窗口。结果表明，以基本块（如阴离子基团和可移动阳离子）为构建块反设计卤化物晶体结构的原理是有效和成功的。对于具有出色输运性能的 P6-NaYCl，模拟结果表明其超离子行为归因于连接两个方向的相干扩散。平面内的迁移路径和沿 方向的迁移路径的同步促进了 NaYCl 中 Na 离子的电导率。我们的研究将促进对卤化物基电解质中输运机制的理解，基于功能基本构建块和特殊堆积模式的结构构建方法将加速无机晶体结构的反向设计。
