Ionic solids and melts are compounds in which the interactions are dominated by electrostatic effects. However, the polarization of the ions also plays an important role in many respects as has been clarified in recent years thanks to the development of realistic polarizable interaction potentials. After detailing these models, we illustrate the importance of polarization effects on a series of examples concerning the structural properties, such as the stabilization of particular crystal structures or the formation of highly-coordinated multivalent ions in the melts, as well as the dynamic properties such as the diffusion of ionic species. The effects on the structure of molten salts interfaces (with vacuum and electrified metal) is also described. Although most of the results described here concern inorganic compounds (molten fluorides and chlorides, ionic oxides...), the particular case of the room-temperature ionic liquids, a special class of molten salts in which at least one species is organic, will also be briefly discussed to indicate how the ideas gained from the study of "simple" molten salts are being transferred to these more complex systems.
Ionic liquids (ILs) gain much interest as possible electrolytes in the next generation of mixed-solid Li-ion batteries. However, such properties of ionic liquids as melting transition, diffusion, strength and structure of hydrogen bond network remain poorly investigated. Here 2H NMR study of a prototypical ionic liquid [TEA][NTf2] has been performed. We show that the dynamical melting occurs through a dynamically heterogeneous phase stable between 223-277 K and the transition process is characterized by two standard molar enthalpy changes indicating to the multistage nature of the melting. The…
We propose a microscopic, first-principles description of the ionic conduction in crystals. This formalism allows us to gain new insights into the ideal characteristics of general ionic conducting materials and, in particular, solid electrolytes. Using \textit{ab initio} calculations, we show that our formalism results in ionic mobilities consistent with experiments for several materials. Our work opens the possibility of developing solid electrolytes based on fundamental physical principles rather than empirical descriptions of the underlying processes.
A Comparative Study of Molecular Dynamics Approaches for Simulating Ionic Conductivity in Solid Lithium Electrolytes
Université de Montréal（蒙特利尔大学）；Mila – Quebec AI Institute（米拉-魁北克人工智能研究所）；National Research Council Canada（加拿大国家研究委员会）；Institut Courtois, Université de Montréal（蒙特利尔大学库尔图瓦研究所）
Drag and diffusion of mobile ions in solids are of interest for both purely theoretical and applied scientific communities. This article proposes a theoretical description of ion drag in solids that can be used to estimate ionic conductivities in crystals, and forms a basis for the rational design of solid electrolyte materials. Starting with a general solid-state Hamiltonian, we employ the non-equilibrium path integral formalism to develop a microscopic theory of ionic transport in solids in the presence of thermal fluctuations. As required by the fluctuation-dissipation theorem, we obtain a …
Direct observation of reversible ionic polarization at a buried solid-state battery interface
Nuclear Physics Institute of Czech Academy of Sciences（捷克科学院核物理研究所）；Slovak University of Technology in Bratislava（布拉迪斯拉发斯洛伐克理工大学）；SRM University-AP（SRM大学安得拉邦分校）；CNR-ITAE（意大利国家研究委员会离子技术及应用研究所）；University of Messina（墨西拿大学）
Molecular dynamics simulation have shown that after initial surface melting, nanowires can melt via two mechanisms: an interface front moves towards the wire centre; the growth of an instability at the interface can cause the solid to pinch-off and breakup. By perturbing a capillary fluctuation model describing the interface kinetics, we show when each mechanism is preferred and compare the results to molecular dynamics simulation. A Plateau-Rayleigh-type of instability is found, and suggests longer nanowires will melt via a instability mechanism, whereas in shorter nanowires the melting front…
Synergetic Enhancement on Bulk and Grain Boundary Ionic Conduction of Mg Doped High-Entropy NASICON-Type Solid Electrolyte for Solid-State Na+ Batteries by Spray Flame Synthesis
Potential jumps at transport bottlenecks cause instability of nominally ionic solid electrolytes in electrochemical cells
电化学装置如固体氧化物燃料电池（SOFC）、固体氧化物电解槽电池（SOEC）和锂离子电池（LIB）的正常操作有时会由于意外形成内相而失败。这些相包括SOEC的氧化锆电解质内的晶界处的氧气泡、全固态LIB的（石榴石型）Li 7 La 3 Zr 2 O 12电解质内的孤立的Li金属岛以及Na-S电池的Na-β-氧化铝和NASICON电解质内的类似Na金属岛。值得注意的是，虽然这些设备可以在两种极性下工作，但故障的倾向取决于极性。在这里，我们解释这些和其他现象在名义上的离子固体电解质和混合导电电极在简单的热力学和动力学方面：意想不到的内部相是由一个大的潜在的跳跃，需要推动一个恒定的离子或电子流通过其内部传输瓶颈。内相形成的明确规则，包括其极性依赖性制定，以帮助预测和减轻它，这将导致微观结构不稳定，效率恶化和击穿。
Halide perovskites have attracted increasing research attention regarding their outstanding optoelectronic applications. Owing to its low activation energy, ion migration is implicated in the long-term stability and many unusual transport behaviors of halide perovskite devices. However, precise control of the ionic transport in halide perovskite crystals remains challenging. Here we visualized and quantified the electric-field-induced halide ion migration in an axial CsPbBr$_3$-CsPbCl$_3$ nanowire heterostructure and demonstrated a solid-state ionic rectification, which is due to the non-unifo…
Electrically induced ionic motion offers a new way to realize voltage-controlled magnetism, opening the door to a new generation of logic, sensor, and data storage technologies. Here, we demonstrate an effective approach to magneto-ionically and electrically tune exchange bias in Gd/Ni$_{1-x}$Co$_{x}$O thin films (x=0.50, 0.67), where neither of the layers alone is ferromagnetic at room temperature. The Gd capping layer deposited onto antiferromagnetic Ni$_{1-x}$Co$_{x}$O initiates a solid-state redox reaction that reduces an interfacial region of the oxide to ferromagnetic NiCo. Exchange bias…
Strain-Dependent Ionic Transport in Li3YCl6 Solid Electrolytes
William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston（休斯顿大学威廉·A·布鲁克夏尔化学与生物分子工程系）；Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China（电子科技大学前沿科学与工程学院）
The interface stresses at of the solid-melt interface are, in general, anisotropic. The anisotropy in the interfacial stress can be evaluated using molecular dynamics (MD) and phase field crystal (PFC) models. In this paper, we report our results on the evaluation of the anisotropy in interface stress in a BCC solid with its melt. Specifically, we study Fe using both MD and PFC models. We show that while both MD and PFC can be used for the evaluation, and the PFC and the amplitude equations based on PFC give quantitatively consistent results, the MD and PFC results are qualitatively the same b…
Predicting Crystal Structures and Ionic Conductivities in Li$_{3}$YCl$_{6-x}$Br$_{x}$ Halide Solid Electrolytes Using a Fine-Tuned Machine Learning Interatomic Potential
Université de Bordeaux, CNRS, Bordeaux INP, ICMCB（波尔多大学，法国国家科学研究中心，波尔多国立高等电子、计算机、电信与无线电通信学院，材料化学与分子物理研究所）；Réseau sur le Stockage Electrochimique de l’Energie (RS2E), CNRS FR 3459（电化学储能网络（RS2E），法国国家科学研究中心）
OBELiX: A Curated Dataset of Crystal Structures and Experimentally Measured Ionic Conductivities for Lithium Solid-State Electrolytes
Mila；McGill University（麦吉尔大学）；University of Ottawa（Ottawa大学）；Technical University of Kenya（肯尼亚技术大学）；National Research Council Canada（加拿大国家研究委员会）；Université de Montréal（蒙特利尔大学）
We study the performance of spin-component-scaled second-order Møller-Plesset perturbation theory (SCS-MP2) for the prediction of the lattice constant, bulk modulus, and cohesive energy of 12 simple, three-dimensional, covalent and ionic semiconductors and insulators. We find that SCS-MP2 and the simpler scaled opposite-spin MP2 (SOS-MP2) yield predictions that are significantly improved over the already good performance of MP2. Specifically, when compared to experimental values with zero-point vibrational corrections, SCS-MP2 (SOS-MP2) yields mean absolute errors of 0.015 (0.017) Å for the la…
