The cathodic performances of V205, Moo3 and MoVzOs were examined to find the best candidate for a rechargeable cathode for lithium cells: in this respect, MoV20s was found to be the most promising. Its main advantage as a cathodic material compared with V205 and MOO, is its good cycling behaviour over a wide voltage range, even when the discharge goes to completion. This good rechargeability may be due to the formation of an amorphous phase as soon as the discharge occurs.
Iutroduction
In the development of rechargeable lithium batteries, increasing attention has been focused on new, mixed oxide-based cathode materials exhibiting high energy density and reversible lithium incorporation. Recently, VzO,--MOO, systems have been proposed as cathode materials in lithium batteries operating at room temperature [ 11. They have been reported to be more promising than their parent oxides VZ05 and Moos. Although V,O, and MOO, undergo intercalation of lithium ions into their crystal lattice, they are not appropriate candidates for secondary lithium batteries because of their poor rechargeability after a deep discharge [2 -61. Extensive lithium insertion can induce irreversible structure reorganization resulting in poor reversible electrochemical performances. Most studies of substitute compounds to overcome this irreversibility have been made using either nonstoichiometric forms such as V60i3, Li1+,V308, and molybdenum compounds intermediate between MOO, and Moos [7 -111, or amorphous compounds such as V20,-P20, glasses [12, 131. Another potentially attractive group of materials for use as high energy lithium cell cathodes is mixed oxide-based systems such as MoVZOs [ 11.