(680c) Revealing Design Principles for an Interphase Layer of Lithium Metal Anodes Via Cryogenic/in-Situ Transmission Electron Microscopy

Over the past decade, lithium metal has been considered the most attractive anode material for high-energy-density batteries. However, its practical application has been hindered by its high reactivity with electrolytes and uncontrolled dendritic growth, resulting in poor Coulombic efficiency and cycle life. It is crucial to comprehend the effect of the solid electrolyte interphase (SEI) on battery performance to develop stable Li metal batteries. Nonetheless, the exact nanostructure and working mechanisms of the SEI remain obscure.
In this presentation, I will share a design strategy for interface engineering using a conversion-type reaction of metal fluorides to evolve a LiF passivation layer and Li-M alloy. Particularly, I propose a LiF-modified Li-Mg-C electrode, which demonstrates stable long-term cycling for over 2,000 h in common organic electrolytes with fluoroethylene carbonate (FEC) additives and over 700 h even without additives, suppressing unwanted side reactions and Li dendritic growth. Furthermore, I will share the relationship between electrolyte components and the structural configuration of interfacial layers using an optimized cryogenic transmission electron microscopy analysis. I revealed a unique dual-layered inorganic-rich nanostructure, in contrast to the widely known simple specific component-rich SEI layers. The origin of stable Li cycling is closely related to the Li-ion diffusion mechanism via diverse crystalline grains and numerous grain boundaries in the fine crystalline-rich SEI layer.