Vacancy-Controlled Na+ Superion Conduction in Na11Sn2PS12
Marc Duchardt, Uwe Ruschewitz, Stefanie Dehnen, Bernhard Roling
备注：
The ion conduction mechanism that is discussed in the article was not verified, so we decided to withdraw the current version of the article. We will think about a replacement once we have gained information about it by means of theoretical studies
Highly conductive solid electrolytes are one key component for the development of safe and high-power all-solid-state batteries. Enormous progress has been achieved in the field of lithium solid electrolytes. Meanwhile, their ion conductivities match those of liquid electrolytes used in commercial Li+ ion batteries. However, the future availability and the price of lithium are points of concern, so that Na+ ion conductors have come into the spotlight in recent years. Here we present the superionic conductor Na11Sn2PS12 consisting exclusively of abundant elements. This material exhibits a room temperature Na+ ion conductivity close to 4 mS/cm, the highest value known to date for sulfide-based solids. Importantly, the stoichiometry of this quaternary compound differs from that of the Li analogues, in derogation from recent theoretical and experimental works. Structure determination based on synchroton X-ray powder diffraction data proves the existence of Na+ vacancies in the tetragonal structure that speed up Na+ ion transport, an untypical mechanism in superion conductors. The results indicate that sodium electrolytes are about to equal the performance of their lithium counterparts. The major target application is clean and safe energy storage, for which the lower energy density of Na+ ion batteries is not a concern, but long-term materials availability and costs are important prerequisites.
Simulations with machine learning potentials identify the ion conduction mechanism mediating non-Arrhenius behavior in LGPS
Li $_{10}$ Ge（PS $_6$）$_2$（LGPS）是一种高度浓缩的固体电解质，其中相邻阳离子之间的库仑排斥被假设为协同离子跳跃的根本原因，协同离子跳跃是诸如Li $_7$ La $_3$ Zr $_2$ O $_{12}$（LLZO）和Li $_{1.3}$ Al $_{0.3}$ Ti $_{1.7}$（PO $_4$）$_{1.7}$（LATP）的超离子导体中常见的机制。虽然使用分子动力学（MD）的第一性原理模拟提供了对Li $^+$传输机制的深入了解，但从历史上看，在模拟和实验中研究的温度范围存在差距。在这里，我们使用了在密度泛函理论（DFT）模拟上训练的神经网络（NN）势，以DFT般的精度运行长达40纳秒的MD模拟，以表征包括先前模拟和实验研究在内的温度范围内的离子传导机制。我们已经证实了锂$^+$亚晶格相变在LGPS约400 K，低于该\textit{ab}平面扩散率$D^*_{ab}$急剧减少。伴随着400 K附近的亚晶格相变，有较少的阳离子-阳离子（交叉）相关性，其特征在于Haven比接近1，并且在较低的温度下，系统中的振动更谐波。直觉上，在高温下，振动模式的收集可能足以驱动协同离子跳跃。然而，在接近室温时，可用的振动模式可能不足以克服静电排斥，从而导致相关性较低的离子运动和相对较慢的离子传导。这种亚晶格相变的现象，在其以下协调跳跃起不太重要的作用，可以…
Understanding the electronic and ionic conduction and lithium over-stoichiometry in LiMn$_2$O$_4$ spinel
采用密度泛函理论和Heyd-Scuseria-Ernzerhof屏蔽杂化泛函，对尖晶石型锂锰氧化物LiMn $_2$ O $_4$中的缺陷热力学和输运进行了第一性原理研究.我们发现，本征点缺陷的LiMn $_2$ O $_4$具有低的形成能，因此可以发生与高浓度。电子传导通过小极化子的跳跃进行，并且离子传导通过锂空位和/或非线性迁移机制发生。总电导率主要由电子贡献决定。发现LiMn $_2$ O $_4$倾向于锂过化学计量，即，锰位锂过量，以及Mn $^{3+}$ /Mn $^{4+}$无序。在LiMn $_2$ O $_4$样品中也可能出现其他缺陷，例如锰反位和空位以及锂杂质。根据我们的研究结果，我们讨论了可能的影响的电化学性能的缺陷，并提供解释的实验观察和缺陷控制的合成和缺陷表征的指导方针。
Vacancy-induced Modification of Electronic Band Structure of LiBO$_{2}$ Material as Cathode Surface Coating of Lithium-ion Batteries
University of Missouri（密苏里大学）；University of Missouri Research Reactor (MURR)（密苏里大学研究反应堆中心）；Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia（哥伦比亚教育技术大学物理学院）
