空间电荷层与卤化物易重排实现卤化物固态电解质界面处的快速锂离子传输
Space Charge Layer and Facile Halide Rearrangement Enable Fast Lithium-Ion Transport at Halide Solid Electrolyte Interfaces
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中文总结 AI 辅助
该研究通过密度泛函理论、分子动力学与光谱实验，揭示卤化物固态电解质异质界面通过空间电荷层和柔性卤化物框架重排协同增强锂离子传导，为设计超离子异质结构提供原子级原理。
中文摘要 AI 辅助
卤化物固态电解质是高能量密度全固态电池的有前景候选材料，因为它们兼具高电压稳定性、易加工性和快速锂离子传导性。最近的一项研究表明，将两种卤化物固态电解质Li$_2$ZrCl$_6$（LZC）和Li$_3$YCl$_6$（LYC）物理混合，相对于单独的LZC和LYC，锂离子电导率分别提高了46%和58%，这表明卤化物异质界面为更快的离子传输提供了一条新途径；然而，这种增强的起源仍然未知。在此，我们结合密度泛函理论计算、缺陷热力学、机器学习驱动的分子动力学以及振动和拉曼光谱，来阐明LZC、LYC及其异质界面中的锂离子传输。利用代表这些卤化物构型无序的低能有序超胞，我们发现Li和Cl间隙原子是两种材料中主要的带电缺陷。形成LZC|LYC界面有利于界面锂弗伦克尔对的生成，在LZC中产生锂间隙原子，在LYC中产生锂空位，从而增加了界面附近的载流子浓度。通过分析相干界面的分子动力学轨迹中Cl围绕金属阳离子的角度取向，我们表明界面创造了新的稳定Cl构型，这些构型适应了伴随锂跳跃的框架重排。模拟的振动功率谱和测量的拉曼光谱表明界面处存在晶格软化和八面体畸变，这与这些Cl构型的形成一致。这些结果支持一种协同机制，其中空间电荷层形成和动态柔性的界面卤化物框架增强了锂离子传导，为超离子卤化物异质结构和多组分固态电解质提供了原子级设计原理。
英文摘要
Halide solid electrolytes are promising candidates for energy-dense all-solid-state batteries because they combine high-voltage stability, facile processing, and fast Li-ion conduction. A recent study showed that physically mixing two halide solid electrolytes, Li$_2$ZrCl$_6$ (LZC) and Li$_3$YCl$_6$ (LYC), raises the Li-ion conductivity by 46% and 58% relative to LZC and LYC, respectively, suggesting that halide heterointerfaces offer a new route to faster ion transport; however, the origin of this enhancement remains unknown. Here, we combine density functional theory calculations, defect thermodynamics, machine-learning-driven molecular dynamics, and vibrational and Raman spectroscopy to elucidate Li-ion transport in LZC, LYC, and their heterointerface. Using low-energy ordered supercells that represent the configurational disorder of these halides, we find that Li and Cl interstitials are the dominant charged defects in both materials. Forming an LZC|LYC interface favors the generation of interfacial Li Frenkel pairs, producing Li interstitials in LZC and Li vacancies in LYC, thereby increasing the charge-carrier concentration near the interface. By analyzing the angular orientations of Cl around the metal cations in molecular dynamics trajectories of a coherent interface, we show that the interface creates new stable Cl configurations that accommodate the framework rearrangement accompanying Li hops. Simulated vibrational power spectra and measured Raman spectra indicate lattice softening and octahedral distortion at the interface, consistent with the formation of these Cl configurations. These results support a cooperative mechanism in which space charge layer formation and a dynamically flexible interfacial halide framework enhance Li-ion conduction, providing atomistic design principles for superionic halide heterostructures and multicomponent solid electrolytes.
发表机构
- Texas Tech University（德克萨斯理工大学）
- University of Texas at Dallas（德克萨斯大学达拉斯分校）
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