Plan-View Operando Video Microscopy of Li Metal Anodes: Identifying the Coupled Relationships among Nucleation, Morphology, and Reversibility

Improving the reversibility of lithium (Li) metal anodes is critical to enable next-generation batteries. However, a comprehensive understanding of the factors that influence the nucleation and dynamic evolution of Li morphology is lacking. In this study, a platform for plan-view operando video microscopy is presented. Using this platform, we quantitatively study (1) differences in the nucleation density of dendrites and pits as a function of current density, (2) the influence of the Li surface grain boundaries on nucleation location, (3) the role of pits formed in the first cycle on dendrite reversibility and extended cycling, (4) the temporal evolution of individual dendrite size, and (5) the impacts of individual dendrite size on “dead Li” formation. The results provide mechanistic insight into the influence of surface spatial heterogeneity on nucleation and growth behavior and suggest that dead Li formation is influenced more by nucleation than by growth.