Electrochemical Properties of Na_0.66V₄O₁₀ Nanostructures as Cathode Material in Rechargeable Batteries for Energy Storage Applications

Abstract

We report the electrochemical performance of nanostructures of Na_0.66V₄O₁₀ as cathode material for rechargeable batteries. The Rietveld refinement of room-temperature X-ray diffraction pattern shows the monoclinic phase with <i>C</i>2/<i>m</i> space group. The cyclic voltammetry curves of prepared half-cells exhibit redox peaks at 3.1 and 2.6 V, which are due to two-phase transition reaction between V^5+/4+ and can be assigned to the single-step deintercalation/intercalation of Na ion. We observe a good cycling stability with specific discharge capacity (measured vs Na⁺/Na) between 80 (±2) and 30 (±2) mAh g^-1 at current densities of 3 and 50 mA g^-1, respectively. The electrochemical performance of Na_0.66V₄O₁₀ electrode was also tested with Li anode, which showed higher capacity but decayed faster than Na. Using density functional theory, we calculate the Na vacancy formation energies: 3.37 eV in the bulk of the material and 2.52 eV on the (100) surface, which underlines the importance of nanostructures.