While intensive efforts have been devoted to studying the nature of the solid-electrolyte interphase (SEI), little attention has been paid to understanding its role in the mechanical failures of electrodes. Here we unveil the impact of SEI inhomogeneities on early-stage defect formation in Si electrodes. Buried under the SEI, these early-stage defects are inaccessible by most surface-probing techniques. With operando full field diffraction X-ray microscopy, we observe the formation of these defects in real time and connect their origin to a heterogeneous degree of lithiation. This heterogeneous lithiation is further correlated to inhomogeneities in topography and lithium-ion mobility in both the inner- and outer-SEI, thanks to a combination of operando atomic force microscopy, electrochemical strain microscopy and sputter-etched X-ray photoelectron spectroscopy. Our multi-modal study bridges observations across the multi-level interfaces (Si/Li_xSi/inner-SEI/outer-SEI), thus offering novel insights into the impact of SEI homogeneities on the structural stability of Si-based lithium-ion batteries.

尽管已投入大量精力来研究固体电解质中间相（SEI）的性质，但很少有人注意了解其在电极机械故障中的作用。在这里，我们揭示了SEI不均匀性对Si电极早期缺陷形成的影响。这些埋藏在SEI中的早期缺陷是大多数表面探测技术所无法企及的。使用全视野衍射X射线显微镜，我们可以实时观察到这些缺陷的形成，并将它们的起源与异质化程度联系起来。由于操作原子力显微镜的结合，这种异质性锂化还与内部SEI和外部SEI中的形貌不均匀性和锂离子迁移率进一步相关，电化学应变显微镜和溅射X射线光电子能谱。我们的多模式研究将跨多级界面（Si / Li_x Si / inner-SEI / outer-SEI），从而提供了关于SEI均匀性对基于硅的锂离子电池结构稳定性的影响的新颖见解。