Origin of graphite exfoliation - An investigation of the important role ofsolvent cointercalation

To elucidate the origin of graphite exfoliation, we have investigated the i nfluence of various material parameters relevant to solvent co-intercalatio n, such as the cation, the electrolytic solvents, and the structure of grap hite, on the solvent decomposition behavior. By electrochemically probing c hanges in the electrode, we demonstrated that a large increase of surface a rea accompanies the decomposition of propylene carbonate (PC). Furthermore. such a change in surface area is dramatically amplified when Li+ is replac ed by tetrabutylammonium ion. A slight structural modification of PC exerts a profound influence on the solvent decomposition behavior, as demonstrate d with cis- and trans-2.3-butylene carbonate. These reaction behaviors are also altered significantly by the choice of graphite. Such an influence of graphite structure is particularly surprising for t-BC electrolyte, in whic h SFG44 graphite undergoes extensive exfoliation, whereas SFG6 graphite and MCMB25 can be cycled reversibly. These results can be best explained by in corporating the co-intercalation of cyclic carbonate as a critical process in the solid electrolyte interphase formation mechanism. (C) 2000 The Elect rochemical Society.