Storage behavior of isomeric quaternary alkyl ammonium cations in graphite electrodes for graphite/activated carbon capacitors

Quaternary alkyl ammonium(QAA) intercalated graphite compounds are promising as efficient and environmentally benign electrode materials in electric energy storage devices. The intercalation and de-intercalation processes of three isomeric QAA cations have been investigated in graphite/activated carbon (AC) asymmetric capacitors based on propylene carbonate (PC) solutions. Some fundamental electrochemical techniques in conjunction with in situ XRD and in situ Raman spectroscopy have been employed to study the differences among them. Isopropyltrimethyl ammonium (iPTMA+) gives the most sluggish interaction with graphite. By contrast, propyltrimethyl and diethyldimethyl ammonium (PTMA+, DEDMA+) demonstrate quicker kinetic behaviors and higher rate capacity in capacitors.