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

The sol-gel synthesis of new chromium–vanadium mixed oxides Cr 0.11V 2O 5.16 Cr 0.06VO 2.09 and Cr 0.33V 6O 13.5 is reported. Their electrochemical properties were investigated for Li insertion. In the case of Cr 0.11V 2O 5.16 (V 2O 5 derived structure), the formation of short CrO 6 octahedra chains linking V 2O 5 layers increases its three-dimensional character. The main electrochemical and structural properties are reported, discussed and compared with those for V 2O 5. The attractive behaviour of Cr 0.11V 2O 5.16 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 Cr 3+ in the V 2O 5 structure leading to a lowering of structural changes and a more reversible character of these structural modifications. The Cr 0.06VO 2.09 oxide (VO 2 (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 Cr 0.33V 6O 13.5 oxide (V 6O 13 type) outperforms stoichiometric and non-stoichiometric V 6O 13.