Sol-gel chromium–vanadium mixed oxides as lithium insertion compounds

The sol-gel synthesis of new chromium–vanadium mixed oxides Cr0.11V2O5.16 Cr0.06VO2.09 and Cr0.33V6O13.5 is reported. Their electrochemical properties were investigated for Li insertion. In the case of Cr0.11V2O5.16 (V2O5 derived structure), the formation of short CrO6 octahedra chains linking V2O5 layers increases its three-dimensional character. The main electrochemical and structural properties are reported, discussed and compared with those for V2O5. The attractive behaviour of Cr0.11V2O5.16 both in terms of specific capacity and cycle life (260 A h/kg after 20 cycles at C/10 rate; 3.8–2 V) can be explained by the doping effect played by Cr3+ in the V2O5 structure leading to a lowering of structural changes and a more reversible character of these structural modifications. The Cr0.06VO2.09 oxide (VO2 (B) type) exhibits a maximum reversible capacity of 320 A h/kg in the potential range 4/1.5 V and a good retention on cycling with a specific capacity of 240 A h/kg after 20 cycles at C/10 rate. The Cr0.33V6O13.5 oxide (V6O13 type) outperforms stoichiometric and non-stoichiometric V6O13.