Synthesis and Characterization of a Cathode Material for Sodium-Ion Batteries Based on a Composite of Sodium Vanadium(III) Phosphate and Expanded Graphite

In this paper, we report an improved solid-state synthesis of Na3V2(PO4)(3) isostructural with the NASICON superionic conductor and ranging in particle size from 0.5 to 4.5 mu m with the use of spray drying of an aqueous solution of precursors, followed by annealing in a nitrogen atmosphere. The specific capacity of a composite of the synthesized Na3V2(PO4)(3) and expanded graphite reaches 117.00 mAh/g at a charge-discharge rate of C/20 and drops to 76.73 mAh/g after 200 cycles in charge-discharge life tests at a charge-discharge rate of 1C. The apparent diffusion coefficient of sodium ions in the solid phase of the Na3V2(PO4)(3)/C composite for deintercalation and intercalation processes is 5.87 x 10(-11) and 4.60 x 10(-11) cm(2)/s, respectively.