Notably, the Na ordering of Na2V2(PO4)3 give rise to a small voltage step (~50 mV). This can be rationalized as the overlap of two biphasic reactions of Na3V2(PO4)3 -Na2V2(PO4)3 and Na2V2(PO4)3 -Na1V2(PO4)3. We note that the two reactions tend to separate more when higher current densities are furnished (Figure ). After that (in region II'' of Figure ), the quantities of Na2V2(PO4)3 and Na3V2(PO4)3 phases diminish, while the Na1V2(PO4)3 content keeps increasing until the end of charge at ~3.75 V vs. Na + /Na. The discharge process down to ~2 V vs. Na + /Na appears rather different (region III). On the plateau, the main reaction seems to occur between Na1V2(PO4)3 and Na2V2(PO4)3 via a twophase reaction. At this stage, the amount of Na3V2(PO4)3 remains low (< 10 wt%).