THE LIXV2O5 SYSTEM - AN OVERVIEW OF THE STRUCTURE MODIFICATIONS INDUCED BY THE LITHIUM INTERCALATION

Depending on the amount of lithium (x) intercalated in V2O5 several structural modifications are observed. For the smallest lithium contents, the alpha-(x<0.01) and epsilon-(0.35<x<0.7) phases exhibit the V2O5 type structure with an increasing puckering of the layers. For the LiV2O5 composition, a gliding of one layer out of two leads to the delta-type structure. All these reactions are fully reversible and the pristine V2O5 phase is recovered upon deintercalation. For intercalation amounts larger than one, the delta-phase is transformed into a gamma-one via an irreversible reconstruction mechanism. the gamma-LixV2O5 phase can itself be reversibly cycled in the 0.0 less-than-or-equal-to x less-than-or-equal-to 2.0 range while maintaining the gamma-type structure. A new metastable variety of V2O5 has been obtained. The intercalation of the third lithium atom in V2O5 leads irreversibly to the formation of an omega-type phase that exhibits a rocksalt type structure. Almost all the lithium can be electrochemically or chemically removed from this material, leading to a unique positive electrode materials for secondary lithium batteries.