A kinetic study of lithium transport in the sol–gel Cr0.11V2O5.16 mixed oxide

The kinetics of the electrochemical lithium insertion reaction in the sol–gel chromium–vanadium mixed oxide Cr0.11V2O5.16 has been investigated using ac impedance spectroscopy. The chemical lithium diffusion coefficient is found to be in the range 10−8/10−12 cm2/s depending the Li content over the wide Li composition range 0 < x < 2 in LixCr0.11V2O5.16. The evolution of the cathode impedance is investigated as a function of the lithium content and cycles. The results are discussed in relation with the cycling properties of the electrode material and the unusual structural response of the sol–gel mixed oxide which consists of a single phase behaviour with a continuous cell volume expansion of 6–7% in the 0 < x < 2 range for LixCr0.11V2O5.16. For x < 1, a comparison with available kinetic data for the parent oxide indicates a very close behaviour. Cr0.11V2O5.16 is shown to be the best V2O5-based cathode material with an initial specific capacity of 280 mAh/g at C/10 rate and still 240 mAh/g after 50 cycles in the 3.8–2 V potential range. The present kinetic data seem to indicate its better cycling behaviour mainly originates from its specific structural response rather than from kinetic reasons.