Abstract

The aim of this article was to improve the solid-phase synthesis of Na3V2(PO4)3/C composite for sodium-ion battery cathode materials using an innovative technique for creating a protective reducing atmosphere, which is formed by incomplete oxidation of carbon fiber during annealing. The resulting Na3V2(PO4)3 phase has a rhombohedral structure of a sodium superionic conductor (NASICON) with particle sizes ranging from 0.5 to 20.0 μm. The encapsulation of Na3V2(PO4)3 granules with a carbon coating leads to a maximum specific capacity of 112.3 mAh g−1 at a charge–discharge rate of C/5 (22.4 mA g−1). After 200 charge–discharge cycles, the synthesized composite demonstrated a specific discharge capacity degradation of 0.107% per cycle. The apparent diffusion coefficients of Na+ ions in the resulting Na3V2(PO4)3/C composite were measured and found to be 5.87 × 10−11 and 4.60 × 10−11 cm2 s−1 for deintercalation and intercalation, respectively.

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