Searching for new anode materials for the Li-ion technology: time to deviate from the usual path

A brief review of our fundamental studies of the reversible reactivity mech anism of vanadates towards lithium is presented. This mechanism totally dif fers from the classical one based either on reversible insertion/deinsertio n of lithium into host structures or on Li alloying reactions, and has led to the thought of using nanosized transition metal oxides as possible negat ive electrode materials for rechargeable Li-ion batteries. Electrochemical capacities, as high as 700 mAh/g with a 100% capacity retention up to 100 c ycles and high rates, can be achieved with optimized metal oxides (MO, M = Co, Cu, Ni, Fe, etc.) powders. By combining transmission electron microscop e (TEM), infrared (IR) and magnetic measurements we directly proved the for mation of 10-50 Angstrom metal nanoparticles dispersed into a lithia (Li2O) matrix during the reduction step of MO with Li. Upon oxidation, the metal nanoparticles were shown to convert back to MO while Li2O was decomposed. T he new opportunities provided by these metal oxides systems based on the re versible formation/decomposition of Li2O are discussed together with the po sitive attributes that nanoparticles could have to the field of energy stor age. (C) 2001 Elsevier Science B.V. All rights reserved.