Nitrogen-doped Carbon Coated Na3V2(PO4)3 with Superior Sodium Storage Capability

Abstract

Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application. Na3V2(PO4)3 is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure. Nevertheless, the practical application of Na3V2(PO4)3 is seriously hindered by its intrinsically poor electronic conductivity. Herein, solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na3V2(PO4)3 cathode material, delivering enhanced electrochemical performances. N-Doped carbon layer coating serves as a highly conducting pathway, and creates numerous extrinsic defects and active sites, which can facilitate the storage and diffusion of Na+. Moreover, the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling. N-Doped carbon coated Na3V2(PO4)3(NC-NVP) exhibits excellent long cycling life and superior rate performances than bare Na3V2(PO4)3 without carbon coating. NC-NVP delivers a stable capacity of 95.9 mA·h/g after 500 cycles at 1 C rate, which corresponds to high capacity retention(94.6%) with respect to the initial capacity(101.4 mA·h/g). Over 91.3% of the initial capacity is retained after 500 cycles at 5 C, and the capacity can reach 85 mA·h/g at 30 C rate.