Recognition of V/V/V Multielectron Reactions in NaV(PO): A Potential High Energy Density Cathode for Sodium-Ion Batteries.

NaV(PO) was reported recently as a novel cathode material with high theoretical energy density for Sodium-ion batteries (SIBs). However, whether V/V/V multielectron reactions can be realized during the charging process is still an open question. In this work, NaV(PO) is synthesized by using a solid-state method. Its atomic composition and crystal structure are verified by X-ray diffraction (XRD) and neutron diffraction (ND) joint refinement. The electrochemical performance of NaV(PO) is evaluated in two different voltage windows, namely 2.5-3.8 and 2.5-4.3 V. V solid-state NMR (ssNMR) results disclose the presence of V in NaV(PO) when charging NaV(PO) to 4.3 V, confirming NaV(PO) is a potential high energy density cathode through realization of V/V/V multielectron reactions.