Graphene-Scaffolded NaV(PO) Microsphere Cathode with High Rate Capability and Cycling Stability for Sodium Ion Batteries.

High voltage, high rate, and cycling-stable cathodes are urgently needed for development of commercially viable sodium ion batteries (SIBs). Herein, we report a facile spray-drying method to synthesize graphene-scaffolded NaV(PO) microspheres (NVP@rGO), in which nanocrystalline NaV(PO) is embedded in graphene sheets to form porous microspheres. Benefiting from the highly conductive graphene framework and porous structure, the NVP@rGO material exhibits a high reversible capacity (115 mAh g at 0.2 C), long-term cycle life (81% of capacity retention up to 3000 cycles at 5 C), and excellent rate performance (44 mAh g at 50 C). The electrochemical properties of a full Na-ion cell with the NVP@rGO cathode and Sb/C anode are also investigated. The present results suggest promising applications of the NVP@rGO material as a high performance cathode for sodium ion batteries.