FORMATION OF THE OMEGA-TYPE PHASE BY LITHIUM INTERCALATION IN (MO, V) OXIDES DERIVING FROM V2O5

Large amounts of lithium have been intercalated electrochemically and chemically in molybdenum-substituted V2O5-deriving phases like the MoyV2-yO5 solid solution (O less than or equal to y less than or equal to 0.60) and Mo6V5O40 (Mo0.8V1.2O5.33). In all cases, the o-type phase is irreversibly formed in the Li3MoyV2-yO5 and Li3Mo0.8V1.2O5.33 compositions. Like in the case of pure V2O5, these new materials exhibit veIy good cycling properties in lithium batteries. Depending on the amount of molybdenum and the potential domain, the specific energy lies in the 900-500 Wh/kg range. The omega-type phases present a rocksalt-type structure with all cations statistically distributed among the octahedral sites, the general formula being Li-x square(0.60-x)Mo(v)V(0.40-v)O (v = y/5) or Li-x square(0.625-x)Mo(0.150)V(0.025)O depending on the starting material. When such materials are formed, for the first time, from V2O5-related phases, they exhibit a superstructure with a tetragonal unit cell. Due to the destabilization of the rocksalt-type lattice for the highest amount of vacancies, the cell voltage increases very rapidly at the end of charge and, therefore, it is impossible to remove the last lithium atoms.