In situ X-ray diffraction of the intercalation of (C 2H 5) 4N + and BF 4− into graphite from acetonitrile and propylene carbonate based supercapacitor electrolytes

Abstract

The intercalation of (C 2H 5) 4N + and BF 4 − from acetonitrile (AN) and propylene carbonate (PC) solutions into bound graphite electrodes during cyclic voltammetry was investigated by in situ X-ray diffraction (XRD) using synchrotron radiation. The disappearance of the 0 0 2 reflection of graphite in the XRD patterns upon intercalation of (C 2H 5) 4N + indicates that the cations are accumulated between the graphene layers. For the intercalation of BF 4 −, the appearance of 0 0 l reflexes in the intercalated state provides clear evidence of staging. In both cases, the in-plane periodicity was not significantly altered by the intercalation process apart from slight changes in the C C bond length. The intercalation of BF 4 − from the PC-based electrolyte was found to have the least destructive effect on the periodicity of the graphite structure during initial cycling in the anodic potential range along with the highest charge/discharge efficiency.