Lithium intercalated compounds - Charge transfer and related properties

Numerous channel- or tunnel-structured compounds are interesting materials in which lithium intercalation occurs primarily without destruction of the host lattice assuming a complete charge transfer. In many cases, the rigid-band model (RBM) is a useful first approximation for describing the changes in electronic properties of the host material with intercalation. The applicability of the rigid-band model is taken as a test for the properties most desirable in a good intercalation material. This review paper presents experimental results, namely optical and electrical measurements, obtained on various intercalation materials such as dichalcogenides, trichalcogenides and oxides to probe the validity of the RBM. The impact of the lithium intercalation is discussed for various structural forms, from well-crystallised to amorphous compounds. We observed, nevertheless, that the rigid-band model is not applicable to all of the layered intercalation materials. This needs yet to be more extensively documented for their promising application as insertion electrode in rechargeable lithium batteries. Compounds such as TiS2, TaS2, MoS2, NiPS3, MoO3, V2O5, V6O13, LiCoO2, LiNiO2, LiMn2O4 and LiNiVO4 are tested in this work. Some guidelines are established for improving the performances of these materials in their most eminent applications. (C) 2002 Elsevier Science B.V. All rights reserved.