The sol–gel chromium-modified V₆O₁₃ as a cathodic material for lithium batteries

Abstract

A new V₆O₁₃-based material has been synthesized via the sol–gel route. This sol–gel mixed oxide has been obtained from an appropriate heat treatment of the chromium-exchanged V₂O₅ xerogel performed under reducing atmosphere. This new compound, with the chemical formula Cr_0.36V₆O_13.50, exhibits a monoclinic structure (C2/m) with the following unit cell parameters, a=11.89 Å, b=3.68 Å, c=10.14 Å, β=101.18°. The electrochemical characterization of this compound has been performed using galvanostatic discharge–charge experiments in the potential range 4–1.5 V and completed by ac impedance spectroscopy measurements. It exhibits a specific capacity of about 370 mAh g⁻¹, which makes the compound Cr_0.36V₆O_13.50 the best one in the V₆O₁₃-based system: 85% of the initial capacity (315 mAh g⁻¹) after the 35th cycle is still available at C/25 without any polarization. From impedance spectroscopy, a high kinetics of Li transport (D _Li=1.8×10⁻⁹ cm² s⁻¹) is found at mid-discharge.