Uniform Carbon Coated Na3V2(PO4)2O2xF3-2x Nanoparticles for Sodium Ion Batteries as Cathode

A uniform carbon-coated Na3V2(PO4)2O2xF3-2x/C (NVPOF/C) nanoparticle synthesize by a novel pyro synthesis method is utilized for sodium-ion batteries (SIBs) as a cathode. Remarkably, the electrochemical properties are performed at high rates show significantly improved discharge capacity. At 0.1 C, NVPOF/C cathode shows a discharge capacity of 130 mAh g-1, corresponding to 100% of the theoretical capacity. Even at 50 C, a discharge capacity of ~85 mAh g-1 could be attained. The in-situ X-ray diffraction and ex-situ synchrotron X-ray absorption near edge structure spectroscopy results exposed that the reversible sodium ion insertion/extraction into/from NVPOF/C host structure occurs with a small volume change (3.4%), indicating the structural stability of the cathode. Our study validates that the Na3V2(PO4)2O2xF3-2x/C electrode is a promising candidate for developing high power/energy density cathodes for SIBs.