AFM study of surface film formation on a composite graphite electrode in lithium-ion batteries

An in situ electrochemical atomic force microscopy (AFM) observation of a composite graphite electrode surface was performed in 1 mol dm(-3) LiClO4 dissolved in a mixture of ethylene carbonate (EC) + diethyl carbonate (DEC), and propylene carbonate (PC) to show the applicability of scanning probe microscopy (SPM) to studies using composite graphite electrodes. In EC + DEC, three kinds of morphological changes (curling, swelling, and exfoliation) in the vicinity of the particle edges were observed in the potential range of 0.8-1.4 V versus Li+/Li. These morphological changes were caused by the intercalation of solvated lithium ions and their subsequent decomposition between graphene layers. On the other hand, vigorous exfoliation and rupturing of graphene layers of the graphite particles were observed at 0.9 V in PC. In addition, deterioration by the formation of holes in the composite graphite electrode was observed in PC, which is attributable to gas evolution upon decomposition of PC molecules. (C) 2003 Elsevier Science B.V. All rights reserved.