Electrochemical lithium insertion in some nickel, zinc and cadmium vanadates

In this work we present a study of the electrochemical characteristics of lithium insertion in eight crystalline Ni, Zn and Cd vanadates. During the electrochemical study carried out down to 0.5 V vs. Li+/Li, CdV2O6 and Cd2V2O7 were found to be the compounds tested accepting the highest number of lithium atoms per metal atom (Li/∑M=1.75 and 1.63, respectively). The zinc and nickel vanadates tested accepted a smaller number of lithium atoms per formula unit. In situ X-ray diffraction experiments showed an almost complete amorphization of the cadmium vanadates at the end of the first discharge while nickel and zinc vanadates were not amorphous. Therefore, these results are in agreement with previous reports of larger lithium atom intake in amorphous than in crystalline materials. In any case, on cycling none of these vanadates perform as well as previously described vanadium compounds.