Near-Shore Aggregation Mechanism of Electrolyte Decomposition Products to Explain Solid Electrolyte Interphase Formation

To get in-Sight of the formation mechanism of solid electrolyte interphase (SEI) film in Lithium-ion battery (LIB), we examine a probable scenario, referred to as surface growth mechanism, for electrolyte involving ethylene carbonate (EC) Solvent and vinylene carbonate (VC) additive by using density functional theory (DFT). We first extracted-stable SEI film components (SFCs) for the EC/VC electrolyte and constructed probable SFC aggregates via DFT molecular dynamics. We then examined their solubility in the EC solution, their adhesion to a model graphite electrode, and the electronic properties. The results showed that the SFC aggregates are characterized by unstable adhesion to the graphite surface and high electronic insulation against the EC solution. These characteristics preclude explaining SEI growth up to a typical thickness of several tens of nanometers based on the surface growth mechanism. With the present results, we propose near-shore aggregation mechanism, where the SFCs formed at the electrode surface desorb into the near-shore region and form aggregates. The SFC aggregates coalesce and come into contact with the electrode to complete the SEI formation. The present model provides a novel perspective for the long-standing problem of SEI formation. (C) The Author(s) 2015. Published by ECS. All rights reserved.