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 μm 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 × 10^–11 and 4.60 × 10^–11 cm²/s, respectively. [ABSTRACT FROM AUTHOR]