ELECTROCHEMICAL STM STUDY ON SURFACE-MORPHOLOGY CHANGE OF HOPG BASAL-PLANE IN AN ORGANIC ELECTROLYTE SOLUTION

To elucidate the mechanism of surface reactions on graphite anodes of lithium-ion secondary batteries, the morphology change of the basal plane of a highly oriented pyrolytic graphite (HOPG) anode in LM LiClO4/ethylene carbonate-diethylcarbonate (1:1 by volume) was observed by electrochemical STM. When the sample potential was stepped to 1.1 V vs. Li/Li+, hill-like structures of ca. 10 Angstrom height appeared on the HOPG surface. The hill-like structure in the vicinity of a step was gradually spread out with time, and a part of it exfoliated. It was considered that the intercalation of solvent is responsible for the formation of the hill-like structure and that this process corresponds to the initial stage of solvent decomposition and subsequent film formation processes.