Ray Connor E, Yao Yi, Galinat Shelby L, Addison Bennett, Blum Volker, Maughan Annalise E
Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, United States.
Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, United States.
Chem Mater. 2024 Sep 25;36(19):9424-9441. doi: 10.1021/acs.chemmater.4c00979. eCollection 2024 Oct 8.
Halide argyrodite solid-state electrolytes of the general formula LiPS exhibit complex static and dynamic disorder that plays a crucial role in ion transport processes. Here, we unravel the rich interplay between site disorder and dynamics in the plastic crystal argyrodite LiPSCN and the impact on ion diffusion processes through a suite of experimental and computational methodologies, including temperature-dependent synchrotron powder X-ray diffraction, AC electrochemical impedance spectroscopy, Li solid-state NMR, and machine learning-assisted molecular dynamics simulations. Sulfide and (pseudo)halide site disorder between the two anion sublattices unilaterally improves long-range lithium diffusion irrespective of the (pseudo)halide identity, which demonstrates the importance of site disorder in dictating bulk ionic conductivity in the argyrodite family. Furthermore, we find that anion site disorder modulates the presence and time scales of cyanide rotational dynamics. Ordered configurations of anions enable fast, quasi-free rotations of cyanides that occur on time scales of 10 Hz at = 300 K. In contrast, we find that cyanide dynamics are slow or frozen in LiPSCN when site disorder between the cyanide and sulfide sublattices is present at = 300 K. We rationalize the observed differences in cyanide dynamics in the context of elastic dipole interactions between neighboring cyanide anions and local strain induced by the configurations of site disorder that may impact the energetic landscape for cyanide rotational dynamics. Through this study, we find that anion disorder plays a decisive role in dictating the extent and time scales of both lithium ion and cyanide dynamics in LiPSCN.
通式为LiPS的卤化物硫银锗矿固态电解质表现出复杂的静态和动态无序，这在离子传输过程中起着关键作用。在此，我们通过一系列实验和计算方法，包括变温同步辐射粉末X射线衍射、交流电化学阻抗谱、锂固态核磁共振以及机器学习辅助分子动力学模拟，揭示了塑性晶体硫银锗矿LiPSCN中位点无序与动力学之间丰富的相互作用，以及对离子扩散过程的影响。两个阴离子亚晶格之间的硫化物和（拟）卤化物位点无序单方面改善了长程锂扩散，而与（拟）卤化物的种类无关，这证明了位点无序在决定硫银锗矿家族中整体离子电导率方面的重要性。此外，我们发现阴离子位点无序调节了氰化物旋转动力学的存在和时间尺度。阴离子的有序构型使得氰化物能够快速、近似自由地旋转，在300 K时旋转时间尺度为10 Hz。相比之下，我们发现在300 K时，当氰化物和硫化物亚晶格之间存在位点无序时，LiPSCN中的氰化物动力学缓慢或冻结。我们在相邻氰化物阴离子之间的弹性偶极相互作用以及由位点无序构型引起的局部应变的背景下，对观察到的氰化物动力学差异进行了合理化解释，这些局部应变可能会影响氰化物旋转动力学的能量格局。通过这项研究，我们发现阴离子无序在决定LiPSCN中锂离子和氰化物动力学的程度和时间尺度方面起着决定性作用。
