用于电池的沸石咪唑酯骨架玻璃电解质中的快速各向同性锂离子扩散
Fast Isotropic Li-Ion Diffusion in Zeolitic Imidazolate Framework Glass Electrolytes for Batteries
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中文总结 AI 辅助
该研究通过机器学习原子间势模拟发现，ZIF玻璃因结构无序使Li⁺扩散活化能降低、扩散系数大幅提升，实现了从晶态的各向异性到玻璃态的各向同性转变，为高性能固体电解质提供了新方向。
中文摘要 AI 辅助
全固态锂电池需要兼具快速室温离子传输、机械坚固性与界面兼容性的固体电解质。沸石咪唑酯骨架（ZIF，属于金属有机框架的一个子集）玻璃是一个具有吸引力但尚未充分探索的平台，因为它们兼具无晶界的非晶拓扑结构与化学可调的骨架。本文中，我们揭示结构无序使ZIF玻璃中实现了快速且各向同性的锂扩散，这一结果通过使用机器学习原子间势模拟Li⁺在晶态和玻璃态ZIF-4、ZIF-62中的传输得以实现。结构无序将Li⁺迁移的活化能从约0.35 eV降至0.16 eV，使ZIF-4的外推室温扩散系数提升一个数量级以上，ZIF-62则提升近七倍。非高斯动力学与范霍夫关联函数分析显示，晶态ZIF中的Li⁺扩散通过罕见、动态异质的跳跃事件在明确的笼间发生；而玻璃态ZIF中的Li⁺扩散更均匀、连续且类似菲克扩散，这得益于配位几何与迁移势垒的宽分布。晶态ZIF中的Li⁺扩散呈强各向异性，反映咪唑环与苯并咪唑环的有序取向在不同晶向施加了截然不同的势垒；玻璃化后，这些环的取向随机化，Li⁺扩散因此变为各向同性或近各向同性。这些发现表明，精心设计的金属有机框架玻璃是高性能固体电解质的有前景候选材料。
英文摘要
All-solid-state lithium batteries require solid electrolytes that combine rapid room-temperature ion transport with mechanical robustness and interfacial compatibility. Zeolitic imidazolate framework (ZIF) glasses, with ZIFs being a sub-set of metal-organic frameworks, offer an attractive yet relatively underexplored platform because they combine an grainboundary-free and amorphous topology with chemically tunable frameworks. Here, we reveal that structural disorder unlocks fast and isotropic lithium diffusion in ZIF glasses. This is realized by using a machine learning interatomic potential to simulate Li+ transport in crystalline and glassy ZIF-4 and ZIF-62. Structural disorder reduces the activation energy for Li+ migration from ~0.35 eV to 0.16 eV and increases the extrapolated room-temperature diffusion coefficient by more than one order of magnitude for ZIF-4 and nearly sevenfold for ZIF-62. Analyses of non-Gaussian dynamics and van Hove correlation functions reveal that Li+ diffusion in crystalline ZIFs occurs via rare, dynamically heterogeneous hopping events among well-defined cages, whereas Li+ diffusion in glassy ZIFs is more homogeneous, continuous, and Fickian-like, benefiting from a wide distribution of coordination geometries and migration barriers. Li+ diffusion in crystalline ZIFs is strongly anisotropic, reflecting that ordered orientations of imidazolate and benzimidazolate rings impose distinct energy barriers along different crystallographic directions. Upon vitrification, these ring orientations become randomized, and hence, the diffusion of Li+ becomes isotropic or near-isotropic. These findings imply that well-designed metal-organic framework glasses are a promising candidate as high-performance solid-state electrolytes.
