Evaluation of the sol-gel mixed oxide Cr0.11V2O5.16 as a rechargeable positive electrode working in the potential range 3.8/1.5 V vs. Li

The electrode features of the sol-gel mixed oxide Cr0.11V2O5.16 have been evaluated here in the potential range 3.8/1.5 V in terms of OCV data, kinetics and cycling properties. This potential range corresponds to the wide Li composition range 0.4 <= x <= 3.2 in LixCr0.11V2O5.16(a = b = 9.23 angstrom, c = 4.08 angstrom). We have demonstrated the omega phase with a tetragonal symmetry is formed when 3.2 Li+ ions enter the host lattice of the mixed oxide and remains stable after oxidation leading to the Li0.4Cr0.11V2O5.16 active phase. The presence of chromium and additional oxygen atoms results in an improvement (10%) of the specific capacity available (350 mA h g(-1)) over 50 cycles in comparison with that achieved with the V2O5 parent oxide. XRD experiments show a high stability of the tetragonal structure at low rate C/20 in good accord with the high specific capacity observed. The ac impedance measurements have proved the cathodic material is characterized by a slower kinetics of Li transport from x > 2 which explains faradaic yields are strongly affected at higher C rate and a decrease in the specific capacity at C/5 rate. Moreover the capacity fading observed at C/5 rate has been correlated with a dissolution process of chromium and vanadium ions in electrolyte. (c) 2005 Elsevier B.V. All rights reserved.