While sodium ion (Na⁺) itself cannot intercalate into graphitic structure to form binary graphite-intercalation-compounds (GICs) as its alkaline brothers (lithium, potassium etc.) do, the intercalation of its solvated form [Na(solvent)_x]⁺ can readily happen, leading to reversible formation of ternary GICs at stage 1, as long as used solvent molecules are stable against reduction, such as ethers. However, a mystery still remains: what causes the initial irreversible capacity loss given that co-intercalation requires an interphase-free surface? In this work, we answered this fundamental question by elaborately examining the solvation structures, desolvation process and the corresponding electrochemical reduction stability of ether-based solvated Na⁺. Based on the understanding, a simple and effective approach was proposed to significantly increase the initial coulombic efficiency of sodium-ether co-intercalation. Such precise control over solvation-sheath and interfacial structures provides molecular-level guidance to the designing of new electrolyte systems and graphite-intercalation chemistries.

尽管钠离子（Na ⁺）本身不能像其碱性兄弟姐妹（锂，钾等）那样嵌入石墨结构以形成二元石墨-嵌入化合物（GIC），但其溶剂化形式[Na（solvent）_x ]的嵌入⁺容易发生，导致阶段1中的三元GIC发生可逆形成，只要所用的溶剂分子对还原稳定，例如醚。然而，仍然存在一个谜：是什么原因导致初始不可逆的容量损失，因为共嵌入需要无界面的表面？在这项工作中，我们通过详尽地研究了醚基溶剂化Na的溶剂化结构，去溶剂化过程和相应的电化学还原稳定性，回答了这个基本问题。⁺。在此基础上，提出了一种简单有效的方法来显着提高钠-醚共嵌入的初始库伦效率。溶剂化鞘和界面结构的这种精确控制为新电解质系统和石墨嵌入化学的设计提供了分子水平的指导。