Impact of Polymer End Groups on the Formation of Solid\nElectrolyte Interphase at the Lithium Metal Interface: A First-Principles\nCalculations Study

The formation and\nstability of the solid-electrolyte interphase\n(SEI) are critical factors influencing the performance and lifespan\nof lithium-ion and lithium metal batteries. In this study, we employ\na combination of density functional theory (DFT) and ab initio molecular\ndynamics (AIMD) simulations to investigate the SEI formation on Li\nanodes and assess the protective properties of different passivation\nlayers. Our theoretical results confirm the experimental observations\nof SEI formation prior to the application of a potential difference.\nWe examine the reactivity of four monomers representing the backbone\nstructure of polymer electrolytes commonly used in solid-state batteries,\nand observe rapid decomposition triggered by charge transfer from\nthe anode to the electrolyte. Additionally, we investigated the impact\nof various well-known inorganic components of the passivation layer.\nAmong these, LiF emerges as the most effective passivation layer,\npotentially providing superior protection for the electrolyte and\nexhibiting the highest energy barrier for the detachment of reactive\noxygen species. Conversely, Li<sub>2</sub>CO<sub>3</sub> demonstrates\ngood electrolyte protection but may exhibit limited Li ion mobility,\nwhile Li<sub>2</sub>O shows a tendency for low protection of the electrolyte.\nThe calculated charge transfer and energy barrier data offer insights\ninto the stability and reactivity of the SEI constituents, suggesting\nthe potential importance of LiF in impeding electron transfer and\npotentially preventing further electrolyte decomposition. Our findings\nprovide additional evidence supporting the significance of increasing\nthe LiF content in the SEI to potentially enhance its performance.