Understanding Electrolyte Decomposition and Interphase Formation at Li Metal Anode in Glyme-Based Electrolytes via...

The stability of the solid electrolyte interphase (SEI) on lithium metal anodes is critical to improving the performance and safety aspects of rechargeable batteries. In this work, density functional theory-based molecular dynamics (DFT-MD) is used to investigate the interfacial decomposition pathways of an equimolar LiTFSI-tetraglyme (G4) electrolyte on the Li(100) surface at 350 and 500 K. The simulations predict a rapid decomposition for the TFSI anion at the interface, while tetraglyme molecules remain intact throughout the simulation. Bader charge analysis and projected density of states (PDOS) calculations show the anode stripping via charge transfer from the Li metal surface to the TFSI anion fragments, driving continuous electrolyte degradation. This study provides atomic-level description into the origin of various SEI components (Li_xF, Li_xO, and Li_xS) in LiTFSI-glyme-based systems. LiF is seen to be the dominant SEI component via TFSI decomposition. No Li₂CO₃ formation is observed during the simulations. The long-timescale (>100 ps) DFT-MD trajectories capture reaction pathways that are not visible at shorter timescales and provide a comprehensive picture of the initiation of solid electrolyte interphase formation. Overall, these findings would help guide the design of more robust and stable electrolytes for lithium-metal batteries.