Effect of surface structure on the irreversible capacity of various graphitic carbon electrodes

In order to understand the structural effect on irreversible capacity, the electrochemical lithium intercalation of various graphitic carbons was stud ied in 1 M LiPF6 solution of ethylene carbonate/propylene carbonate/diethyl carbonate (EC/PC/DEC), as a function of PC content. Because the irreversib le capacity was increased by PC only for the carbons with a considerable ed ge fraction, it was possible to selectively amplify and monitor the reactio n on the edge surface. The important role of the edge surface was confirmed qualitatively by high resolution transmission electron microscope images o f the surface structure and quantitatively by further analysis on the resul ts, using a simple model that explicitly considered the different reactivit y of EC and PC toward the basal and edge surfaces. Exfoliation behavior, em erging as the PC content increased above a certain structure- dependent thr eshold, was examined also. The structural effect could be explained by assu ming that the cointercalation of PC gave rise to exfoliation. Two controlli ng factors were suggested: the structural integrity affecting the expansion of layer spacing and the geometry of the edge surface affecting the cointe rcalation of PC. (C) 1999 The Electrochemical Society. S0013-4651(98)03-036 -5. All rights reserved.