In-Situ Studies on the Electrochemical Intercalation of Hexafluorophosphate Anion in Graphite with Selective Cointercalation of Solvent

Abstract

Electrochemical cells utilizing graphite intercalation compounds at both electrodes have been proposed as an energy storage technology where the electrolyte salt is split and stored in the electrodes on charge and reformed on discharge. The anion intercalation compounds of graphite proposed as cathodes in these systems have been studied in electrolytes that are resistant to oxidation at 5 V but that are incompatible with graphite anodes. Recent work has demonstrated that electrolytes based on monofluoroethylene carbonate (FEC) and ethylmethyl carbonate (EMC) have superior oxidative stability on graphite cathodes over previously studied electrolytes and form a stable solid electrolyte interphase (SEI) on graphite anodes that allow for full dual-graphite cells to be evaluated for energy storage applications. There is still a limited understanding as to structure of the anion intercalate formed in these electrolyte systems and the effect of solvent cointercalation on cathode performance. This effort was unde...