Early Stage Li Plating by Liquid Phase and Cryogenic Transmission Electron Microscopy

Li metal anodes are among the most promising options for next-generation batteries, exhibiting the highest theoretical capacity. However, irregular Li electrodeposition, which raises safety concerns, is a major obstacle in practical applications. Therefore, a fundamental understanding of the beginning phases of Li plating, such as nucleation and early growth, which have a decisive influence on the dendritic growth of Li, is essential. In this study, we investigated the early stage of Li plating at the single-particle level and its correlation with the solid-electrolyte interphase (SEI) using in situ liquid phase transmission electron microscopy (TEM) and cryogenic TEM. We observed contrasting nucleation dynamics and particle growth patterns in two electrolytes (1 M LiPF6 in ethylene carbonate/diethyl carbonate and 1 M LiTFSI in 1,3-dioxolane/dimethoxy ethane), which originate from different chemical and physical properties of the SEIs. Based on our findings, we propose a mechanism of nucleation and initial growth of Li dictated by the SEI.