STM Study of Well-Defined Graphite/Electrolyte Interface Polarized in Propylene Carbonate Solution Containing 12-Crown-4

Abstract

Surface morphology change of highly oriented pyrolytic graphite was investigated in 1 M (M = mol dm−3) LiClO4 dissolved in propylene carbonate (PC) and PC + 0.5 M 12-crown-4 using electrochemical scanning tunneling microscopy to elucidate the mechanism of passive film formation on graphite electrode in rechargeable lithium batteries. In PC, vigorous exfoliation of graphite layers was observed after potential cycling down to 0 V vs. Li/Li+. Such exfoliation was greatly suppressed by 12-crown-4 addition. The original step structure was nearly maintained, but swellings of graphite surface appeared after potential cycling. From these results, the role of 12-crown-4 in passive film formation was discussed.