Investigation of sodiation performance in Na₃V₂(PO₄)₃/C nanoflakes as a cathode in sodium-ion batteries

Sodium-ion batteries are a next-generation and cost-effective alternative to rechargeable lithium-ion batteries. However, the energy density of the battery is driven by its cathode and using sodium ion as a carrier limits its capacity, cycle life and rate capability. In this work, we explore the enhancement in the electrochemical performance of Na₃V₂(PO₄)₃/C (NVP/C) as a promising cathode material in SIBs. Sodium vanadium phosphate is a NASICON-type structure and, thus, shows less strain during intercalation and de-intercalation of sodium ions. NVP/C has been prepared through the sol-gel method, and its detailed material characterization has been carried out. The powder XRD pattern confirms the phase purity for NVP/C indexed using JCPDS no. 53-0018. The morphological investigation shows grains of size 20-50 nm. Various electrochemical measurements- EIS, CV, galvanostatic cycling, etc. were carried out in the coin cell half-cell configuration. The CV curves show sharp redox peaks as 3.45/3.29 V attributed to V⁺³/V⁺⁴. The multiple peaks during reduction suggest the transfer of Na⁺ ions from Na(1) to Na(2) site. The charge-discharge profile provides a specific capacity of 89.25 mAh/g at 2C and a coulombic efficiency of 99.85%. Also, various Ex-situ characterization techniques, like FESEM, AFM, etc., will be recorded to analyze the morphology and subsequent roughness of the electrode before and after cycling.