In situ analysis of the interfacial reactions between MCMB electrode and organic electrolyte solutions

The interfacial phenomena between graphite (mesocarbon-microbeads (MCMB)) electrode and organic electrolyte solution were analyzed by in situ atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. The influence of lithium salts (anion species), LiPF6, LiBF4, and LiClO4, on the interfacial reaction, including lithium intercalation into graphite, was investigated in EC + DMC solutions. In situ AFM observation disclosed that morphological changes are quite different from one another depending on the kind of lithium salt (anion). A large expansion of MCMB particle was observed particularly in LiPF6/EC + DMC. An expansion of MCMB particle started above 1.0 V versus Li/Li+ and this expansion seemed to be caused by the decomposition of ternary graphite intercalation compound (GIC) (CnLi(sol)(y)), because the expansion remained after de-intercalation of lithium. IRAS spectra of each electrolyte solution showed different behaviors and different reduction products of solvents. double modulation FTIR (DMFTIR) spectra on graphite electrode, which emphasize the surface species, indicated relatively small changes after cathodic polarization. Therefore, the observed morphological changes were caused mainly by the expansion of graphene layers and not by the precipitation of reduction products. (C) 2002 Elsevier Science B.V. All rights reserved.