Electrospun Na3V2(PO4)3/C nanofibers as stable cathode materials for sodium-ion batteries

Abstract

Sodium-ion batteries are considered as prime alternatives to lithium-ion batteries for large-scale renewable energy storage units due to their low cost and the abundance of sodium bearing precursors in the earth's mineral deposits. In the current work, a 3D NASICON framework Na₃V₂(PO₄)₃/carbon cathode electrode with 20–30 nm Na₃V₂(PO₄)₃ nanoparticles uniformly encapsulated interconnecting one-dimensional carbon nanofibers was fabricated using a simple and scalable electrospinning method. The Na₃V₂(PO₄)₃/C cathode showed an initial charge capacity of 103 mA h g⁻¹ and a discharge capacity of 101 mA h g⁻¹ (calculated on the total mass of Na₃V₂(PO₄)₃ and carbon) at 0.1C rate, and retained stable discharge capacities of 77, 58, 39 and 20 mA h g⁻¹ at high current densities of 2C, 5C, 10C and 20C, respectively. Moreover, because of the efficient 1D sodium-ion transport pathway and the highly conductive network of Na₃V₂(PO₄)₃/C, the electrode exhibited high overall capacities even when cycled at high currents, extending its usability to high power applications.