Raman Spectroscopy for Understanding of Lithium Intercalation into Graphite in Propylene Carbonated-Based Solutions

Electrochemical lithium intercalation within graphite was investigated in propylene carbonate (PC) containing different concentrations, 0.4, 0.9, 1.2, 2.2, 2.8, 3.8, and 4.7 mol dm−3, of lithium perchlorate, LiClO4. Lithium ion was reversibly intercalated into and deintercalated from graphite in 3.8 and 4.7 mol dm−3solutions despite the use of pure PC as the solvent. However, ceaseless solvent decomposition and intense exfoliation of the graphene layers occurred in other solutions. The results of the Raman spectroscopic analysis indicated that contact ion pairs are present in 3.8 and 4.7 mol dm−3solutions, which suggested that the presence of contact ion pairs is an important factor that determines the solid electrolyte interphase- (SEI-) forming ability in PC-based electrolytes.