PVP-modulated synthesis of NaV₆O₁₅ nanorods as cathode materials for high-capacity sodium-ion batteries

Highly uniform NaV₆O₁₅ nanorods were obtained via a facile and low-cost PVP-modulated hydrothermal process. It is largely accepted that such a unique feature is favorable for rapid diffusion for sodium ions according to the intrinsic crystal structure. As the cathode, the as-prepared NaV₆O₁₅ nanorods are capable of delivering a high initial capacity of approximately 157 mA h g⁻¹ at 20 mA g⁻¹ for potentials ranging from 1.5 to 3.8 V and yielding 121 mA h g⁻¹ at a high current density of 200 mA g⁻¹. EIS analysis results demonstrated that the diffusion coefficients D _Na as high as 2.71 × 10⁻¹² cm² s⁻¹ at room temperature. In addition, it could be clearly observed that the NaV₆O₁₅ exhibited metallic behavior from the electron density of states, providing excellent electron conductivity. All these results suggest that NaV₆O₁₅ nanorods can be a very promising cathode for sodium batteries.