Interfacial insights for divergent dendrite formation mechanisms in lithium and magnesium anodes

Abstract

Dendrite formation in Li-ion batteries poses safety risks and current density constraints due to potential short-circuiting. Understanding dendrite formation mechanisms is crucial for designing effective strategies. Inspired by the divergent dendrite formation behaviors between Li and Mg anodes, this study investigates the underlying mechanisms, focusing on solid electrolyte interphase (SEI) interfacial properties. Various Li-SEI and Mg-SEI components, including Li₂O, LiF, Li₃N, Li₂CO₃, Li₂S, MgO, MgCl₂, and Mg(OH)₂, are considered. Two key factors—metal plating tendency on SEI surfaces and electron transfer tendency across the anode/SEI interface—are explored. We find that interfaces with minimal lattice mismatch are more favorable than those based solely on surface energy considerations. Additionally, SEI-symmetrized interfaces, where the plating metal grows with SEI symmetry, are compared with heterogeneous interfaces. Our results reveal significant differences between Li-SEI and Mg-SEI compounds in facilitating electron transfer and plating tendencies. Li-SEI compounds, except LiF, generally promote dendrite formation, while Mg-SEI compounds, especially MgO(100) and MgO(111), hinder electron transfer or make metal plating less favorable, reducing the likelihood of Mg dendrite formation. This distinction suggests that Mg anodes are less prone to dendrite issues, promoting more uniform ion deposition on anode surfaces and enhancing battery stability. Our analysis highlights the importance of SEI interfacial properties in dendrite formation, providing insights for designing innovative SEI layers to mitigate these challenges.