An efficient sodium-ion battery consisting of reduced graphene oxide bonded Na3V2(PO4)3 in a composite carbon network

Abstract Sodium-ion batteries have been considered as the most promising candidate for large-scale energy storage applications. However, the poor cycling stability and inferior rate capability of existing cathode materials for sodium-ion batteries restrict future developments. Herein, we report a chemically bonded cathode material for sodium-ion batteries that is synthesized by freeze-drying and subsequent annealing to generate Na3V2(PO4)3/reduced graphene oxide−carbon nanotubes (NGC) composite. The NGC composite with 79 wt % Na3V2(PO4)3 shows a high initial Coulombic efficiency (>93%) and high specific capacity with superior cycling stability (∼105 mAh g−1 after 500 cycles at 1 C based on the mass of Na3V2(PO4)3). More importantly, in situ electrochemical impedance spectroscopy and ex situ X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption near edge structure spectroscopy, and transmission electronic microscopy are employed to reveal the robust V−O−N bonding and excellent sodium storage performance of the NGC composite.