A cell employing a graphite cathode and a molybdenum (VI) oxide (MoO3) anode is investigated as a possible energy storage device. Graphite cathode allows raising the voltage well above the cathode materials of LIBs without causing safety issues. The bottom potential of this anode is 2.0V vs. Li/Li+, which is well above the lithium plating potential. Pulse polarization experiment reveals that no lithium deposition occurs, which further enhances the safety of the graphite/MoO3 full cell. Charge/discharge mechanism of this system results from intercalation and de-intercalation of the PF6 − in the cathode (KS-6) and Li+ in the anode (MoO3). This mechanism is supported by in situ X-ray diffraction data of the graphite/MoO3 cell recorded at various states of charge.