We report on electrochemical reactions of a variety of metal fluorides (TiF3, VF3, MnF2, FeF2, CoF2, NiF2, CuF2, CaF2, BaF2), metal oxides (TiO, TiO2, VO2, V2O3, V2O5, NbO, NbO2, Cr2O3, RuO2, MoO3), TiS2, and TiN with lithium in nonaqueous lithium cells over a wide voltage range (0.02-4.3 V) at room temperature. In most cases, deep Li uptake occurs via heterogeneous reaction resulting in transformation of MXm (M = transition metal; X = F or O or S or N) into a nanocrystalline or amorphous LiXm/n/M composite from which Li can be extracted under restoration of the MXm phase. Thermodynamic and kinetic aspects, especially overpotential and its possible origins for both Li uptake and Li extraction processes, are discussed. (C) 2004 The Electrochemical Society.