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

Abstract

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 Li ϩ 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.

Behavior of Graphite Electrodes in Solutions Based on Ionic Liquids in In Situ Raman Studies

“…16,[18][19][20] The aim of the present work was to study the behavior of the graphite electrodes in 1-methyl-1-propyl-pipperidinium bis͑trifluo-romethylsulfonyl͒imide ͑MPP p TFSI͒, containing 1 M LiTFSI with the emphasis on understanding phenomena such as cointercalation and passivation. For this purpose, we used an in situ Raman microprobe technique, which is an especially well-suited tool for the study of the intercalation processes into graphite, in conjunction with electrochemical measurements.…”

“…[14][15][16][17][18] In general, it can be said that a reversible Li intercalation into graphite electrodes can take place only when the kinetics of their passivation by surface films is faster or occur at higher potentials than that of the possible cointercalation of solution species ͑together with Li ions or alone͒, as may be the case with IL cations, and which is usually destructive for graphite particles. 16,[18][19][20] The aim of the present work was to study the behavior of the graphite electrodes in 1-methyl-1-propyl-pipperidinium bis͑trifluo-romethylsulfonyl͒imide ͑MPP p TFSI͒, containing 1 M LiTFSI with the emphasis on understanding phenomena such as cointercalation and passivation. For this purpose, we used an in situ Raman microprobe technique, which is an especially well-suited tool for the study of the intercalation processes into graphite, in conjunction with electrochemical measurements.…”

Multiwalled Carbon Nanotubes Resist Intercalation Whereas Pyrolytic Graphite Can Exfoliate in Propylene Carbonate: Electroanalysis Without the Deleterious Effects of Intercalation for the Detection of Ammonia

“…In particular considering TBAP as supporting electrolyte, [16,17] the TBA þ and ClO 4 À ions are reported to cointercalate into graphite layers with the solvent. Due to the insertion of a large cation TBA þ into the graphite layer the expanded space is thought to further facilitate the insertion of PC.…”

Improvement of electrochemical characteristics of natural graphite negative electrode coated with polyacrylic acid in pure propylene carbonate electrolyte

“…Around this potential, the co-intercalation of Li + ion solvated with PC molecules occurs, resulting in the reductive decomposition of PC as described in the literature [11]. It was considered that the graphite layer was exfoliated because Li + ions and PC molecules were co-intercalated into it as described below.…”