In Operando Probing of Sodium-Incorporation in NASICON Nanomaterial: Asymmetric Reaction and Electrochemical Phase Diagram

NASICON-type materials are one of the most promising cathodes for sodium-ion batteries (SIBs) due to their stable structure and the three-dimensional framework for the migration of Na+. During the usage of SIBs, they should hold the ability to endure sudden changes in temperature and current density, which have a profound impact on battery life. However, little research focused on the reaction mechanism under the above situations. Here, the phase transformation processes of NASICON-type material, Na3V2(PO4)3, are investigated by applying high-resolution in situ X-ray diffraction and Raman coupled with electrochemical tests under different temperatures (273 and 293 K) and scan rates (0.5, 2, and 5 mV s–1). The results demonstrate that the phase evolution process is one-phase solid solution during the desodiation process rather than the traditionally two-phase reaction at a high scan rate or low temperature. An electrochemical phase diagram is also drawn based on thein situ results, which can be used to exp...