Na₃V₂(PO₄)₃/C nanorods as advanced cathode material for sodium ion batteries

Abstract Morphological control is an effective way to improve the electrochemical properties of electrode materials for rechargeable batteries. In this paper, 1D Na₃V₂(PO₄)₃/C nanorods were successfully synthesized by a facile electrospinning method. Using as the cathode of sodium ion batteries, the Na₃V₂(PO₄)₃/C nanorods display good electrochemical performance. For example, it shows quite a flat potential plateau around 3.4 V (vs Na⁺/Na) and delivers an initial capacity as high as 116.9 mAh g^{- 1} at current density of 0.05 C, which is close to the theoretical capacity of 117.6 mAh g^{- 1}. When cycled at 0.5 C, the initial discharge capacity is 105.3 mA h g^{- 1}, and 92.6% of this value is still retained after 50 cycles. The good electrochemical performance can be ascribed to the short ion diffusion distances induced by the 1D nanorod morphology. The sodium ion diffusion coefficient of Na₃V₂(PO₄)₃/C nanorods after the first cycle is 5.39 × 10^{- 13} cm²/s, which is one order higher than the irregular micron scale Na₃V₂(PO₄)₃/C reported before.