Effect of Surface Structure of Graphite on the Passivation Ability of Solid Electrolyte Interphases

Abstract

Solid electrolyte interphase (SEI) layer that forms on the graphite negative electrodes of lithium-ion batteries (LIBs) has a crucial role in inhibiting the excess decomposition of electrolyte solutions. While this passivating ability is essential for improving the durability of LIBs, the relationship between the passivating ability and the surface structure of the graphite is not yet fully understood. In this study, we investigate the solvent co-intercalation behavior in the presence of SEI layers formed on various types of graphite surface structures. The amount of edge sites on each graphite sample is determined using electric double layer capacitance. The co-intercalation reactions of untreated, ethylene-carbonate-treated, and vinylene-carbonate-treated graphite samples in dimethoxyethane-based electrolyte solutions are compared. The co-intercalation reactions commence at approximately 1 V vs. Li/Li⁺ for all untreated samples, but the onset potentials are lowered by the presence of SEI layers, and the extent of this lowering depends on the sample. The SEI layer formed on the edge-rich surface effectively suppresses the co-intercalation reaction, and the additive is also more effective for the edge-rich sample.