Lithium metal batteries (LMB) have high energy densities and are crucial for clean energy solutions. The characterization of the lithium metal interphase is fundamentally and practically important but technically challenging. Taking advantage of synchrotron X-ray, which has the unique capability of analyzing crystalline/amorphous phases quantitatively with statistical significance, we study the composition and dynamics of the LMB interphase for a newly developed important LMB electrolyte that is based on fluorinated ether. Pair distribution function analysis revealed the sequential roles of the anion and solvent in interphase formation during cycling. The relative ratio between Li₂O and LiF first increases and then decreases during cycling, suggesting suppressed Li₂O formation in both initial and long extended cycles. Theoretical studies revealed that in initial cycles, this is due to the energy barriers in many-electron transfer. In long extended cycles, the anion decomposition product Li₂O encourages solvent decomposition by facilitating solvent adsorption on Li₂O which is followed by concurrent depletion of both. This work highlights the important role of Li₂O in transitioning from an anion-derived interphase to a solvent-derived one.

中文翻译：

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实验和理论研究揭示的锂金属界面成分的演化和相互作用

锂金属电池（LMB）具有高能量密度，对于清洁能源解决方案至关重要。锂金属界面的表征具有根本性和实用性，但在技术上具有挑战性。利用同步加速器 X 射线具有定量分析具有统计意义的结晶/非晶相的独特能力，我们研究了新开发的基于氟化醚的重要 LMB 电解质的 LMB 界面的组成和动力学。对分布函数分析揭示了循环过程中阴离子和溶剂在界面形成中的顺序作用。在循环过程中，Li ₂ O 和LiF之间的相对比率先增加然后减少，这表明在初始循环和长期延长循环中Li ₂ O 的形成均受到抑制。理论研究表明，在初始循环中，这是由于多电子转移中的能垒造成的。在长周期中，阴离子分解产物Li _{2 O通过促进溶剂吸附在Li 2} O上来促进溶剂分解，随后两者同时耗尽。这项工作强调了 Li ₂ O 在从阴离子衍生界面向溶剂衍生界面转变中的重要作用。