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

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 (similar to 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. (C) 2018 Elsevier B.V. All rights reserved.