Implementation of high-energy-density lithium metal batteries are hampered by safety hazards like degradation of the solid electrolyte interphase (SEI) and dendrite growth, necessitating rational understanding and modification of SEI building blocks. Especially, the intrinsic role of one of its main components, lithium fluoride (LiF), has been debated with uncertainty. Herein, we present that highly lithiophilic impurities (like N, O, CO₃) contribute towards the elusive amorphous LiF phase stability. This can be linked to their strong interaction with Li, forming well-dispersed lithium-sheathed clusters that help distort the LiF local structure surrounding them. Furthermore, a significant interplay is observed between transformation in Li-F chemical bonding and its structural distortion. Mechanically, our findings suggest that remarkable ductility is achieved by an informed choice regarding the distribution of constituent impurities in LiF. In essence, the physical origin of highly sought-after interfacial characteristics in LiF is discussed, clarifying the composition effect on phase change.

高能量密度锂金属电池的实施受到固体电解质界面（SEI）降解和枝晶生长等安全隐患的阻碍，因此需要对 SEI 构建块进行合理的理解和修改。特别是，其主要成分之一氟化锂 (LiF) 的内在作用一直存在争议。在此，我们介绍了高度亲锂的杂质（如 N、O、CO ₃) 有助于难以捉摸的非晶 LiF 相稳定性。这可能与它们与 Li 的强烈相互作用有关，形成分散良好的锂鞘簇，有助于扭曲它们周围的 LiF 局部结构。此外，在 Li-F 化学键合转变与其结构变形之间观察到显着的相互作用。在机械方面，我们的研究结果表明，通过对 LiF 中成分杂质的分布做出明智的选择，可以实现显着的延展性。本质上，讨论了 LiF 中备受追捧的界面特征的物理起源，阐明了成分对相变的影响。