Study of lithium insertion into MexV2O5+x/2, Me = copper, iron or chromium

Transition metal vanadates, containing copper, iron or chromium, with the stoichiometry (MeV2O5+x/2)-V-x where Me = Cu, Fe and/or Cr, and a monoclinic-brannerite structure were formed by thermal decomposition of hydrated metal vanadates (Me(VO3)(2) . 2H(2)O) above 550 degrees C. Intercalation of lithium into composite electrodes containing a 85:10:5 mixture of (MeV2O5+x/2)-V-x, graphite and polytetrafluoroethylene gave initial specific capacities in the 0.4-0.7 Ah/g range to 1.0 V versus lithium (0.7-1.3 Wh/g). The specific capacity fade over the first few cycles was largely caused by structural changes taking place in the (MeV2O5+x/2)-V-x structure. The capacity and reversibility of transition metal vanadates was related to the transition metal ion present in the order Cu > Cr > Fe. They had reasonable reversibility towards lithium intercalation with higher capacities compared to vanadium based oxides studied in the past. (C) 1997 Elsevier Science S.A.