Foss Carl Erik L, Talkhoncheh Mahdi K, Ulvestad Asbjørn, Andersen Hanne F, Vullum Per Erik, Wagner Nils Peter, Friestad Kenneth, Koposov Alexey Y, van Duin Adri, Mæhlen Jan Petter
Department of Battery Technology, Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller, Norway.
Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
J Phys Chem Lett. 2025 Mar 6;16(9):2238-2244. doi: 10.1021/acs.jpclett.4c03620. Epub 2025 Feb 21.
For the past decade, silicon (Si) as a material for negative electrodes of Li-ion batteries has been considered among the most promising candidates for replacing commonly used graphite. However, Si-based electrodes suffer from severe degradation, which depends on the type of Si materials used. Generally, the degradation of Si is mainly viewed in terms of particle fracturing during lithiation accompanied by constant growth of the solid electrolyte interphase (SEI). At the same time, the reversed process, delithiation, has received little attention. The present work demonstrates the morphological changes of the Si components of electrodes occurring during electrochemical cycling through electron microscopy analyses. These changes are rationalized through the migration of Si, resulting in the formation of Si dendrites embedded in SEI. With the assistance of ReaxFF modeling, we demonstrate that the delithiation predominantly drives this process. The present study reveals that fracturing of Si particles is not the only cause for degradation, as the Si surfaces dramatically change after prolonged cycling, resulting in the formation of Si dendrites.
在过去十年中，硅（Si）作为锂离子电池负极材料一直被认为是替代常用石墨的最有前途的候选材料之一。然而，硅基电极会严重降解，这取决于所使用的硅材料类型。一般来说，硅的降解主要从锂化过程中的颗粒破碎以及固体电解质界面（SEI）的持续生长方面来看待。与此同时，脱锂这一相反过程却很少受到关注。目前的工作通过电子显微镜分析展示了电化学循环过程中电极硅成分的形态变化。这些变化通过硅的迁移得到合理解释，导致形成嵌入SEI的硅树枝晶。在反应分子动力学（ReaxFF）模型的辅助下，我们证明脱锂主要驱动了这一过程。本研究表明，硅颗粒的破碎并非降解的唯一原因，因为长时间循环后硅表面会发生显著变化，导致形成硅树枝晶。
