Origin of Graphite Exfoliation An Investigation of the Important Role of Solvent Cointercalation

To elucidate the origin of graphite exfoliation, we have investigated the influence of various material parameters relevant to solvent co‐intercalation, such as the cation, the electrolytic solvents, and the structure of graphite, on the solvent decomposition behavior. By electrochemically probing changes in the electrode, we demonstrated that a large increase of surface area accompanies the decomposition of propylene carbonate (PC). Furthermore, such a change in surface area is dramatically amplified when is replaced by tetrabutylammonium ion. A slight structural modification of PC exerts a profound influence on the solvent decomposition behavior, as demonstrated 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 which SFG44 graphite undergoes extensive exfoliation, whereas SFG6 graphite and MCMB25 can be cycled reversibly. These results can be best explained by incorporating the co‐intercalation of cyclic carbonate as a critical process in the solid electrolyte interphase formation mechanism. © 2000 The Electrochemical Society. All rights reserved.