The feasibility of a pyrrolidinium-based ionic liquid solvent for non-graphitic carbon electrodes

The feasibility of a pyrrolidinium-based room-temperature ionic liquid (RTIL) as the solvent for lithium-ion batteries is tested by analyzing its intercalation behavior and thermal stability. The RTIL-cations are intercalated into a graphitic carbon and a part of them are irreversibly trapped inside the graphene layers. These trapped cations block Li⁺ intercalation to give only a marginal capacity. In contrast, such a cation insertion/trapping is absent in two non-graphitic carbons; hard carbon and soft carbon. A stable cycle performance with a Li⁺ insertion capacity of about 200 mAh g ^{- 1} is attained. The absence of RTIL-cation insertion is evidenced by the cyclic voltammograms and Raman spectra. A calorimetric study reveals that this RTIL has a higher thermal stability and less reactivity with lithiated carbons as compared with the carbonate-based solvent. The use of this RTIL solvent for the non-graphitic carbons seems to be feasible.