Graphite intercalation of bis(trifluoromethanesulfonyl) imide and other anions with perfluoroalkanesulfonyl substituents

Abstract

Graphite intercalation compounds (GICs) containing the bis(trifluoromethanesulfonyl) imide anion, C xN(SO 2CF 3) 2, were prepared under ambient conditions in 48% hydrofluoric acid, using the oxidant K 2MnF 6. Within seconds, the graphite phase was no longer observed, and a stable, stage 2 product with x = 37 and d i = 8.1 Å was obtained in 15 min. Product compositions were evaluated by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and elemental analyses. One-dimensional structural refinement for the stage 2 product provided values for the graphene carbon/intercalant molar ratio, distance between graphene and sulfonate oxygen planes, and the anion orientation within the intercalated galleries. Intercalation reactions with the larger fluoroanions bis(pentafluoroethanesulfonyl) imide (CF 3CF 2SO 2) 2N −, trifluoromethanesulfonyl- n-nona-fluorobutanesulfonyl imide (CF 3SO 2)(CF 3(CF 2) 3SO 2)N −, and tris(trifluoromethanesulfonyl) methide (CF 3SO 2) 3C − occurred but were dramatically slower. For each product, stages and d i were determined for the mixed phase products. In all cases with the larger anions, the products obtained also contained unreacted graphite.