Hexafluorophosphate anion intercalation into graphite electrode from methyl propionate

The electrochemical intercalation of hexafluorophosphate anion into a graphite positive electrode from methyl propionate (MP) has been investigated by conventional electrochemical techniques in conjunction with in situ Raman spectroscopy and ex situ X-ray diffraction. Graphite electrodes could deliver stable reversible specific capacities higher than 100 mAh g− 1 in MP-based solutions at room temperature. Furthermore, the storage/release of PF6− anion into/from graphite electrodes becomes facilitated in MP-based solutions at a very low temperature, as compared with other solvents, such as propylene carbonate (PC) and ethyl methyl carbonate (EMC). The effect of LiPF6 concentration has also been addressed. The solvation states of the anion in the MP solutions were analyzed by nuclear magnetic resonance and infrared spectroscopy.