In situ Raman spectroscopic analysis of solvent co-intercalation behavior into a solid electrolyte interphase-covered graphite electrode

Solid electrolyte interphase (SEI) on a graphite-negative electrode plays an important role in lithium-ion batteries. The roles of the SEI involve a passivation of a solvent co-intercalation reaction, but why the SEI can suppress the solvent co-intercalation reaction is not fully understood. In this study, the solvent co-intercalation behavior against various SEI-covered graphite electrodes was investigated using cyclic voltammetry and in situ Raman spectroscopy. Ethylene carbonate (EC)-treated, vinylene carbonate (VC)-treated, and untreated graphite electrodes were compared in a dimethoxyethane (DME)-based electrolyte solution. Whereas the DME co-intercalation constantly proceeded from 1.2 to 0.6V versus Li/Li+ for the untreated graphite electrode, the co-intercalation was relatively suppressed above 0.8V versus Li/Li+ for the EC-treated and VC-treated graphite electrodes. Below 0.7V versus Li/Li+, the VC-treated electrode exhibited higher passivation ability than the EC-treated one. In addition, the co-intercalation behavior in electrolyte solutions containing an SEI-reagent in advance was also investigated. In this case, the passivation ability was further improved. [GRAPHICS] .