Reversible Potassium Vanadium Bronze Cathodes (K(X)V6O(13+Y)) with VariousPotassium to Vanadium Ratios

摘要

Electrodes composed of crystalline K(x)V6O(13+y), where x is from 0 to 3.6 and yfrom 0 to 3.8, were prepared by thermal decomposition at 300-350 C of electrochemically deposited (NH4)(x)K(4-x)V6O16 phases. The reversible lithium insertion into these materials was measured under cyclic voltammetry and constant current conditions. Phase changes during discharge resembled those of V2O5 or V6O13 for similar vanadium oxidation states and small K/V ratios. The reversible capacity decreased as the K/V ratios increased from 0.1 to 0.5 and was poor above 0.5 (Li/V less than 0.1). The reversible capacity of the bronzes improved for lower O/V ratios and the discharge voltage was similar to non stoichiometric V6O13. Best cycle life was obtained for non stoichiometric vanadium oxides with K/V ratios in the range of 0.05 to 0.3 for O/V ratios between 2.4 and 2.5. Over 50 cycles at the C-rate were obtained (only 5-10 percent of the capacity lost at 0.4 e(-)/V depth of discharge).