Impacts of fluorine in NASICON‐type materials as cathodes for aqueous zinc ion batteries

Abstract

Abstract Sodium superionic conductor (NASICON)‐type materials are getting more and more attention due to their high capacity and good cycling ability compared with other cathode materials in aqueous zinc ion batteries (AZIB). The present paper was to study the synthesis and electrochemical properties of two NASICON compounds of Na3V2(PO4)3 and Na3V2(PO4)2F3 and to understand the impacts of fluorine. Both Na3V2(PO4)3 and Na3V2(PO4)2F3 are synthesized by hydrothermal growth followed with annealing at 800°C in inert gas. With 3 mol/L Zn(CF3SO3)2 in water as electrolyte, Na3V2(PO4)3 offered a high storage capacity, while Na3V2(PO4)2F3 demonstrated a high discharge voltage though low storage capacity. It was also found that the storage capacity of Na3V2(PO4)2F3 increases with increased cycles; however, the compound undergoes a gradual phase transition. It is discussed possible approaches to attain both high discharge voltage and large capacity with good cycling stability.