It is crucial to suppress lithium dendrite formation in lithium metal batteries. Formation of a good solid–electrolyte interphase (SEI) has been considered to be effective in limiting lithium dendrite growth. However, how the SEI may be modified during lithium deposition is hard to resolve due to challenges in in situ investigation of the SEI with fine details. We report an in situ study that uncovers the lithium dendrite suppression mechanism arising from SEI modification by a poly(diallyldimethylammonium chloride) (PDDA) cationic polymer film, using electrochemical liquid cell transmission electron microscopy (TEM). Lithium nanogranules are obtained in the presence of the polymer film. Chemical mapping of the deposits provides remarkable details of the SEI on individual nanogranules. It shows that lithium fluorides are uniformly distributed within the inner SEI layer of individual lithium nanogranules, arising from the instantaneous reaction of the deposited lithium with PF₆⁻ ions accumulated by the cationic polymer film, and thus the dendritic growth of lithium is prohibited. The ability to directly measure SEI chemistry at the nanoscale down to the individual nanograins in situ and unveil its correlation with the lithium deposition behavior opens future opportunities to explore unsolved mechanisms in batteries.

中文翻译：

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揭示了阳离子聚合物薄膜诱导的固-电解质界面改性对锂枝晶的抑制作用

抑制锂金属电池中锂枝晶的形成至关重要。良好的固-电解质中间相（SEI）的形成被认为可以有效地限制锂枝晶的生长。然而，由于在现场对SEI进行精细研究的挑战，难以解决如何在锂沉积过程中对SEI进行修饰的问题。我们就地报告这项研究利用电化学液体电池透射电子显微镜（TEM）揭示了由聚二烯丙基二甲基氯化铵（PDDA）阳离子聚合物薄膜对SEI进行改性而引起的锂枝晶抑制机理。锂纳米颗粒在聚合物膜的存在下获得。沉积物的化学图谱提供了各个纳米颗粒上SEI的显着细节。结果表明，氟化锂均匀地分布在单个锂纳米颗粒的内部SEI层中，这是由于沉积的锂与PF _6-的瞬时反应引起的^。离子通过阳离子聚合物薄膜积累，因此禁止了锂的树枝状生长。直接测量从纳米级到原位单个纳米颗粒的SEI化学并揭示其与锂沉积行为的相关性的能力为探索电池中未解决的机理提供了未来的机会。