Synthesis of Na3V2(PO4)2F3@V2O5-x as Cathode Material for Sodium-ion Battery

Low energy/power density and inferior cycling stability are bottlenecks to restrict the applications of sodium-ion batteries. Recently, coating the surface of cathode material by metal oxides containing oxygen vacancies, was regarded as an effective strategy to improve electrical conductivity and power/energy density. In this study, Na3V2(PO4)(2)F-3@V2O5-x, nanosheets were synthesized via hydrothermal strategy followed by heat treatment. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis were applied to investigate the structure of Na3V2(PO4)(2)F-3@V2O5-x. As a cathode of sodium-ion batteries, Na3V2(PO4)(2)F-3@V2O5-x, delivers excellent cycling stability and rate capability. It exhibits an initial discharge capacity of 123 mAh.g(-1) at 0.2C, and a discharge capacity of 109 mAh.g(-1) after 140 cycles. At 1C, its initial reversible capacity is 72 mAh.g(-1), which remains 84% after 500 cycles. The outstanding electrochemical property could be ascribed to its enhanced sodium-diffusion and improved electronic conductivity induced by disordered surface coating. Furthermore, it encourages more investigations into practical sodium-ion battery applications.