Reactivity and Evolution of Ionic Phases in the Lithium Solid–Electrolyte Interphase

The unstable solid–electrolyte interphase (SEI) on Li anodes is the origin of major performance challenges in batteries, namely, insufficient Coulombic efficiency (CE) and cycle life. While it known that SEI participates aging processes, pinpointing chemical origins by tracing them to specific phases has been experimentally challenging. Here, we formed single-phase, thin (<50 nm) interfaces Li2O or LiF—the two most common ionic phases—on investigated their stability upon immersion ether- carbonate-based electrolytes. Contrary some conventional wisdom are stable, find electrochemical impedance X-ray spectroscopy SEI|electrolyte can undergo significant evolution. DOL/DME electrolytes impart minimal changes, organic/F-rich layers evolve at between LiF carbonate electrolyte containing LiPF6 salt, exacerbating subsequent plating overpotentials. results suggest selection important improve transport ionic-rich interfaces.