The charge−discharge behaviors of natural graphite in propylene carbonate (PC):dimethyl carbonate (DMC) mixed solutions were investigated after a solid electrolyte interface (SEI) was formed in an ethylene carbonate (EC)-based electrolyte. Electrolytes consisting of LiClO 4 /PC and PC:DMC (1:1 by vol) caused a continuous decomposition of solvents, which led to the exfoliation of graphite. On the other hand, LiClO 4 /PC:DMC (1:7 by vol) showed successful charge−discharge curves without the exfoliation of graphite. These results indicate that the mixing ratio of PC:DMC plays an important role in suppression of the exfoliation of a graphite electrode. Raman spectra of the electrolytes show that the solvation numbers of PC molecules per lithium ion differ drastically in PC:DMC (1:1 by vol) and PC:DMC (1:7 by vol) due to the selective solvation of PC molecules. These results indicate that the solvation number of PC molecules per lithium ion is an important factor in determining the charge−discharge behavior of graphite in PC-based electrolyte.
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Yamada et al. (2009) studied this question.