First-principles study of ethylene carbonate adsorption on prismatic hard carbon surface: An insight into solid-electrolyte interphase formation

Solid-electrolyte interphase (SEI) formation at the hard carbon-based anode of sodium-ion batteries (SIBs) is a key process determining the cycling performance of batteries. In this work, we investigate the initial process of SEI formation on hard carbon by performing first-principles calculations considering solvation effect within the joint density functional theory framework. Using the constructed slab models, we consider adsorption and subsequently decomposition of an ethylene carbonate (EC) molecule on the graphite prismatic surfaces with the armchair and zigzag edges, calculating the relevant energy profiles. Our calculations reveal that the physical adsorption of EC molecule on the graphite surfaces is exothermic with negative adsorption energies, which is interpreted by electronic charge redistribution upon EC adsorption, showing significantly large amount of charge transfer under fluid condition with fixed potential at 0.8 V. Under the same condition, the energy profiles for decomposition of EC molecule on the surfaces are obtained, finding that the reactions are overall exothermic with reasonable activation barriers of at least 0.41 eV. Through clarifying the mechanism of SEI formation, we believe this work can contribute to optimizing electrolyte for SIBs.